i am buying an Iroc Z with a tpi. Ive never owned a TPI mine is TBI so i dont know much about them. Ive heard you cant do as much upgrading to them without messing up the computer. What are some upgrades i could to gain HP but still leave the car moslty stock?

 

Definitely upgrade the entire exhaust system. What year is the 305TPI?

 

best upgrade..and the most worth it is a 350

 

Do all the free mods and you'll be surprised. Fix the stuff that GM didn't design right in the first place.

 

Good Start would be a simple Throttle Body bypass......

 

well its an 85 Iroc Z. What kind of headers and exhaust system would you recommend?

 

headers and exhaust,
3.42 gears
afpr
180 thermostat
prom tuning, on 85 tpi cars the computer was the worst;
and if you want to spend some money get the heads ported and put the bigger valves in,

 

I've got the same car. Check my sig for a list of mods that I did.

 

well, this all depends... ::takes a deep breath::
if you live in a state (like mine) that requires smog stuff, then i suggest that you go wth headers that have AIR tubes and you will most deffinatly need a set with a O2 bung in it. I suggest shorttie headers. IF you get shorties, make sure they come with a y pipe. If you dont have to worry about the smog ****'s, then your choice's are a little bit broader because you no longer need to look for the AIR hook up on the headers. I also suggest that when you get headers, get them coated with a cermaic coating for protection against the heat that the headers will give off. It will save you a lot of time and money on replacing wire boots to starters. Also you will find that headers come in different primary sizes. From 1 1/2 in. to 1 3/4 in... The best for a 305 is 1 5/8ths inch. The most popular companies are Hooker, Heddman, SLP, and Edelbrock. They are all good but some will flow better then others. Heddman makes both with AIR and w/o air headers. the ones w/o air are the cheapest, but do not have a y pipe, but no fear, heddman makes a y pipe for them. Hooker makes headers with and with out air tubes. They are a little bit more money then the heddmans. If you have deeeep pockets, SLP is awesome. Stainles Steel, AIR tubes, y pipe and in both 1 5/8ths and 1 3/4's... with them coated and instalation kit... your looking at upwards of over $800... ok now that the headers is out of the way... cat back ::another deep breath::
Cat backs are basicly what ever you are wanting in noise factor. Loud, mild, silent... what have you... You can go from flowmaster set up to your own dual exhaust set up. and if you need a cat, i suggest you get a hi flow one... it will flow just as well as no cat. Since i am a hooker ***** (weird huh?) i love hooker and i suggest that you listen to Mark A Shields's sound clip. The more i hear the hooker cat back, the more i cant wait till i get it installed on my car. Flowmaster is nice, but doent flow as well, and to me, doesnt sound as nice... i like a mean sound.. Other cat backs can be found from Borola (sp?), edelbrock, MAC, Banks (they do make one, just gotta find it), Mufflex, Ravin (midas i belive?), and SLP. Its basicly up to what you plan on spending. If you have no budget... i say SLP headers with a 3in cat and Borola(sp?) exhaust. If you are on a budget, and you dont need AIR stuff, then do what im doing (suggestion) and go with Heddman's shorties with y pipe, coated, and with hooker cat back. ok... im spent... its 2am... ouch.. gunna hurt in the morning... (or when i wake up)

 

As far as cat-back systems go, I can definitely recommend the Hooker Aerochamber 3" cat-back exhaust. I installed one on my IROC-Z last year and it's everything that I wanted. It's not very loud at idle, but once the car opens up it sounds amazing. Keep in mind that I still have the stock exhaust manifolds and Y-pipe, so that is limiting some potential noise. The Aerochamber muffler is, as the name states, a chambered muffler. Meaning, there's no gauze or anything inside to burn up and make the exhaust sound "hollow" over time. The only change in exhaust you'll hear as time goes on is the breaking in of the catalytic converter. After about three months, my Catco high-flow cat was broken in and the exhaust was a tad louder.

Right now, I'm torn between Hedman and Hooker for my header choice. Both companies offer great products. I think I'm leaning towards Hooker simply to keep my exhaust all one brand (not that it matters, though). I'm probably going to have a Y-pipe custom made because I'm going to run a header dump and I really don't want to hack up a brand new Y-pipe.

 

Thanks for all the advice..ill take it into consideration when i do my upgrades here in the near future.