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Exhaust is the most important change for these cars.  Check out the black magic project truck to see the affects the exhaust had on its performance and Camaros have an even worse exhaust design than the trucks.

2. The air cleaner. http://www.thirdgen.org/newdesign/tech/ultimatetbi.shtml The snorkel on the TBI camaro is too small for a 2.8L V6 much less a 5L V8. Easiest fix is to replace it with a 3" tall 14" diameter open element filter with a flat base. You can drill a hole in the base to put your IAT sensor in. Also toss the choke collar that is between the TBI and the air cleaner assembly. Good for around 10hp. 

Another nice setup can be seen here http://91rsramair.tripod.com/ for colder air input.

Here are the Summit racing air filters that I recommend and use.

SUM-239421 14 in. diameter, chrome, flat base, 2in. element, air cleaner assembly for tight clearance hoods

SUM-239431 14 in. diameter, chrome, flat base, 3in. element, air cleaner assembly

3. Modify the throttle body. This one pretty cheap but does require removing the throttle body. http://www.thirdgen.org/newdesign/tech/ultimatetbi2.shtml NOTE: I recommend using two injector pod gaskets instead of trying to fabricate one thicker one. You may need longer bolts to put the pod back on. Good for 5hp but helps with the more mods that you make. 

With 350's I typically recommend going 46-50mm from www.rvmorsemachine.com depending on the head and cam combination your planning on using with the 350.

4. Intake and cam (with valve springs). I put these 2 together since you have to remove the intake to replace the cam. The valve springs are important since the stock Camaro TBI redlines at 5k.  With proper cam and valve springs redline can easily be 6000 rpm or higher. Stock TBI intake is just a bad design. The edelbrock performer 3704 TBI intake (for the trucks) is a good EASY replacement. It will bolt right up and work. You can also use the Holley Projection TBI intake which flows more air but is harder to get the throttle linkage to work.  For more performance, mainly for modified 350's, use a carb intake with a TBI to carb adapter which both Jegs and Summit Racing sell. But it does require some fabrication to make them work and you can pretty much guarantee you won't get a EGR valve to work.  First, it's a carb intake and thus requires an adapter. Jegs sell adapter for $40. Next it requires fabricating a throttle cable bracket and sometimes a remote coil mount but the hp difference is worth the effort if you are going to change heads (more on that later).

NOTE: 91-93 B-Body cars (Caprice, Roadmaster) have a larger distributor hole in the intake than any other GM car.  The distributor thus has a larger base on it and won't fit down a standard intake distributor hole.  This was done so the distributor would have more room to go in at a steeper angle due to the motor sitting so far back in the engine compartment.  If your going to use an aftermarket intake, take that intake and distributor to a machine shop and have that hole enlarged to match your distributor.

The cam in the TBI engine is just plain AWFUL. Specs on Stock TBI cam is .050" tappet lift (intake/exhaust) is 179/194; and maximum lift with 1.5:1 rocker ratio (intake/exhaust) is .350/.384. I highly recommend a used roller cam from a LT1 camaro Z28. They can be found inexpensively and have great specs for a TBI engine. Specs for LT1 The duration at lash point in degrees at .050" tappet lift (intake/exhaust) is 205/207; and maximum lift with 1.5:1 rocker ratio (intake/exhaust) is .447/.459. Valve lash is zero/zero and lobe centerline is 116 degrees. If you a need a recommendation for a cam, just shoot me an email at sales@tbichips.com with your engine and car specs and I would be glad to recommend a cam for you.. Intake and cam is worth a good 40hp as long as you did the other mods too.

If your using a 350 that has a flat tappet cam then check out www.tbichips.com/truckmods.htm for cam choices.

5. The Heads. The TBI heads are the worst flowing heads GM ever released. So the best bang for the buck is the World Class SR torquer II heads. They have a 305 set and a 350 set. They flow well and are not real expensive for an aftermarket head. The GM Vortec head is also a good choice but does require a special intake and lots of EGR work if you need EGR to remain emission legal. These heads are good for a solid 50hp.  Also check out the aluminum heads on ebay. http://motors.shop.ebay.com/items/?_nkw=sbc+heads+pair+aluminum

Check out the heads on http://www.rhsheads.com/Products/Heads/PT-SBC.asp Vortec heads that flow more than stock vortecs and have a bolt pattern for a standard intake and the price isn't much more than a new stock set of vortecs.  I haven't had a chance to use them but they should be great for the $$.

6. The TBI unit. The stock 305 and 350 TBI unit has 2 (1 11/16") bores which flow 450 cfm of air. Compared to a 650 Holley carb that is bad. Holley does make an aftermarket TBI unit for the truck that will work with the cars with a little work and it has 2" bores and 65lb/hr injectors. It flows 670 cfm of air and good on a 350 or with aftermarket heads. I know longer recommend using a 454 throttle body.  Too many issues with different TPS sensor and rewiring the IAC valve and the throttle bodies just being wore out.  Get your TBI bored out at www.rvmorsemachine.com It may cost a little more but I feel you will have less headaches.

One of my customers http://stores.ebay.com/TBIPARTS  now carries a lot of TBI parts including a pigtail to use the 454 throttle bodies on the 4.3, 305, or 350 wiring harness.and www.rvmorsemachine.com can bore those 50mm 454 throttle bodies to 54mm for the most air currently available for TBI.

7. Injectors. GM released 5 sizes of TBI injectors (actually more but those are the important ones) 40lb/hr for the 4.3L and 5L engines, 55lb/hr for 350 engines, 65lb/hr for cop car 350 engines and (80lb/hr and 90lb/hr) for 454 engines. Depending on how much horsepower you make you may need on of the other injectors. I have been recommending www.injectors4u.com for injectors lately.

Instead of using adjustable fuel pressure regulators which has been all the rage in the past.  I have tested several springs and had a custom spring http://motors.search.ebay.com/18-psi-spring made that will yield 17-18psi at a much lower cost than buying a regulator and a fuel pressure gauge to set that regulator by.   This way you can just slap the spring in and go and its a one time disassembly of the throttle body instead of 3 or 4 times to get the fuel pressure correct.

Also,  a new fuel pump  http://motors.search.ebay.com/?from=R40&satitle=dynapex+fuel+pump  is VERY important as  the stocker is only good for about 250hp and won't maintain any higher fuel pressure. It can barely keep the fuel pressure maintained for the stock 9-12 psi. 

So what size injector or fuel pressure combo to use?  Well here is a basic guideline.

305 up to 200hp the 305 injectors are fine.  If you go more than that which pretty much a cam upgrade and exhaust will do then upgrade to the 350 truck injectors.

Stock 210hp 350 V8 up to 240hp the stock 55lb 350 truck injectors at the factory 9-12psi is fine.

from 240hp to 260hp the fuel pressure should be bumped up to 13-14psi on stock 350 truck injectors which will change their flow rating to 60lb/hr

From 270hp to 320hp you need to change the fuel pump as the stock pump can't maintain pressure over 270hp and you need to run 18psi on the 350 truck injectors for a flow rate of 68lb/hr

From 320-360hp this is where you should be looking at the 454 injectors and run them at the 13psi for their 82lb/hr flow rate.  You can run them at the stock 9-12psi and still be fine for this power range.

From 360-400hp you need to bump the fuel pressure up on the 454 injectors to the 18 psi to increase their flow rate to 96lb/hr.

For over 400hp you really should be looking at alternative injection system but for up to 450hp you would need to run 24psi of fuel pressure to increase the lb/hr rating on 454 injectors to 112lb/hr and that is as much pressure as I recommend applying to a set of TBI injectors.

8. Of course there is the 350 block. 350's have a better bore to stroke ratio than the 305 making the 350 easier to get the HP. Scoggin Dickey Chevrolet sells a nice BRAND NEW L98 shortblock 350 for $1200 that would make a great base engine for a TBI car. The oil pan timing chain and such parts are interchangeable between the 305 and 350. I do recommend the 350 harmonic balancer. You also need the 350 knock sensor and ESC (Electronic Spark Control module) for a 89 Caprice classic with 350. At least 55lb/hr injectors are a must for the 350. http://www.sdpc2000.com/cart.asp?action=prod_detail&catid=514&pid=620

Check Out Blueprints 383 short block $2000 for a nice base for your 383 project. http://www.blueprintengines.com/popular_configurations/index.html?topic=specs&pc_id=78  

 9. The chip. Depending on how many of these modifications you do the more the need for a custom chip or chips.  No matter what you do you are going to need a chip of sort (the stock chip is just too wimpy).  Whether it is my base STAGE 1 chip or a custom burned chip for those major modifications.

10. GEARS.  The automatics came with the 2.73 gear ratio and the 5speeds 3.08.   You can change to 3.42 gears and preferably posi at the same time and your car will be MUCH quicker and will only cost you about 2-3mpg at most and runs great on the highway.  I wouldn't recommend the 3.73 unless you have at least gotten as far as the cam swap in your modifications.  The stock power band is just too low in the rpm band to take advantage of the 3.73 gear. For the automatic cars go to http://www.transmissioncenter.net/speedometer_calibration_______va.htm to get the gears to recalibrate your speedo.

11. Torque converter for you automatic lovers.  The stock converter stalls at 1400-1600 rpm which is very low.  The 95+ S10 4.3L V6 torque converter stalls 2000-2200 rpm.  That 600 rpms will help keep your engine in its powerband and thus make it faster.  If you go with a pretty much any cam upgrade then a higher stall would be advised for most applications. The 2000 rpm stall  is a good upgrade that won't screw up your gas mileage, burn up your trans, break the budget, or be unbearable on the street.

12. Oil pumps, I have decided to add this on the list as TOO many people when building engines put high volume oil pumps in their motors and don't do this for a few reasons. 1. you would need to run a 7qt oil pan or you will suck the stock pan empty with any spirited use.  2. It takes 20hp to turn a high volume pump at higher rpms over a std volume pump. 3. Unless you prep the block properly you will end up sending too much oil to the hydraulic lifters and pump them up too much causing vacuum issues and poor performance.  I use a std volume, high pressure pump http://www.summitracing.com/parts/MEL-M55A/ and its better than stock TBI oil pump and will save us both a LOT of headaches.

None of this stuff if done correctly will ruin your gas mileage.  Properly tuned you shouldn't get less than 23 mpg on the highway with cruise set (no leadfooting).  In town however gas mileage is directly affected by the lead foot attached.  All that new found power may adversely affect your gas mileage as you flex your muscle.

Some good competition Cams.  Choose one that provides the rpm range that you want your engine to run in.  Whether you have a flat tappet or roller cam in your car/truck any of those options will run well in your TBI engine.  All 87+ cars got roller cams but the trucks didn't get one until 1996 (Vortec).  The trucks have all the provisions for the roller equipment but just didn't get the parts.