I just bought a 1991 RS with the 305 TBI in it. The car is in excellent shape with only 39K miles on it. After driving it for a week, I developed an acute need for more horsepower.
These are the details: The car is currently 100% original. I have already purchased a K&N filter with an open element kit that will go on this weekend. I bought the car to use for my daily commute. I drive about 75 miles each day; half 80 mph express way, half 45 mph stop and go. I have set a budget of around $1000.00 give or take. The car currently runs smooth. It leaks nothing.
I am moderately mechanically capable (i.e. if I have good directions, I usually don’t destroy things), but have never torn into an engine before. I have a reasonable set of tools, but nothing specialized for automotive work. Time is usually my limiting factor, and as I said, I need this thing to run on Monday mornings.
I want gut wrenching acceleration, but I also want to get at least 100K miles out of this car, so I need a balance.
I have considered nitrous, heads, exhaust, pistons, TBI mods, chips, fuel pump, frame stiffening, wiring, etc, but I don’t know what combo will serve me best.
You guys have been there, done that, and put out the fires. Let me know what's best.

 

well, first things first, (you already have the open element), I'd go exhaust, frees up horse power and mpg, don't forget the free mods on the home page

 

I'm sure you'll be able to get 100k easy. The L03 holds up over time pretty well. I'm assuming you want to keep gas milage, so exhaust headers on back will be your best bet. It won't make your car a speed demon, but should free up 20-25 hp as well as better gas milage. Ignition mods are always good in terms of milage and throttle response. An MSD 6AL, power coil, cap and rotor, and 8.5mm wires will do wonders. Once you start going beyond these mods to make power, the milage starts to drop.

 

Yeah, I would start with a full exhaust. Its expensive but anyone on here that has done it will tell u it was well worth the money.

1. Headers: Get either the Edelbrock TES Headers but get the part number EDL-6872 I know they say for a 305 TPI IROC-Z but they will fit on ur car fine and it comes with a 3" collector at the y-pipe which is good for exhaust system. Or you can go with the SLP 1-5/8" Headers which are awesome headers but are a little pricey but worth it from what I hear. I went with the Edelbrocks and I Like them so its up to u.

2. Get the Headers and Y-pipe Coated: Jet-hot will do them for 125 bucks I think. Well worth it in the long run. Will keep ur headers looking like new for life and cools them down so ur engine is cooler too. Plus they look so shiney.

3. Gaskets & Bolts: Don't use the gaskets that come with ur headers. Get a set of copper gaskets. That way u will never have to worry about an exhaust leak. And if u want even more insurance, get the Stage 8 locking bolts. I love mine. The copper gaskets run 32 bucks and so do the bolts.

4. Cat or No Cat: You can either chop that bad boy off and put in a straight 3" steel piping like I did for 5 bucks or you can buy a hi-flow cat with 3" in and 3" outlets for 100 bucks. I like the 5 buck idea better though. Its ur choice.

5. Cat-back exhaust: Last but not least is the cat-back. Get a 3" cat-back. Hooker, Flowmaster and SLP make some pretty nice 3" cat-backs. Its your choice. They comes with everything.

Well thats your exhaust system. It will cost a good dollar but will give u a very nice sound and a lot more hp/tq.


Also a mod I really liked was replacing my rear end gears and open differential with an SLP limited slip differential.

I am not sure which u have now but when I did a burn out only one tire spun...aka open differential. SLP Sells limited slip differentials for 99.95 and I Love mine. Also, get a set of either 3:42 or 3:73 GM Motive Gears. You will be amazed how much of a difference down low you will get from just replacing your old 2:73 gears. Get your gears from www.gearsareus.com and the differential is at www.slponline.com or just go right here
http://www.slponline.com/view_produc...TNUMBER=64501T

Either way u go first, rear end or exhaust your gonna love the difference. Good luck and when u get done with those things, move onto to the next big project. I suggest though that you do the ultimate tbi mods to free up some horsepower. I know a guy who will do all of them and add an injector spacer for 40 bucks. Real cool guy. He ran a 13.10 in the 1/4 mile with his 305 TBI and thats the fastest I have seen for that engine/injection system. His e-mail is camaroracer1992@yahoo.com Give him a yell. Good luck.

Oh and I made a page just for people like you who are going into modding their 305 TBIs for the first time. It has every mod I have ever done ( a lot adds up over 4 years) and it has pictures, descriptions, part numbers, do's and don'ts and installation instructions and contacts for all your mods. Its the second site in my sig. If u have any questions, make a post or e-mail me. If I don't know the awnser, I probably know someone that does. Lata

 

exhaust, gears help but if you drive 80 mph alot i wouldnt go too deep. tune up with good ignition items. others can add more