My buddy has a 91 IROC-Z 350 TPI, the car runs very poorly. THe symptoms are:it runs very rich, a lot of carbon in the throttle body,its sputters and back fires especially when it is floored,a lot of times when its floored it shoots out a lot of black smoke and it wants to die when it is started.
We are not sure where to even start working on this and dont want to spend a lot of money replacing unessecary things. We checked the timing and it was at 10 so we moved it down to 8 and so far no difference. Any ideas PLEASE HELP. THANKS

 

Test the fuel pressure. When you do, you'll be removing he fuel pressure regulator vacuum line, so you can determine if the regulator is leaking through at that point.

Another thing to check is the PCV system.

Let us know what the fuel pressure reading is.

 

Ok I have a lot of updates. I posted this and didnt know exactly what he had on his car. Heres what he has: TPIS min ram,comp cam but he is not sure on the duration or lift,23 degree trick flow heads with gold 1.5 rocker arm and a new computer. He is going to change the spark plugs, distributor cap and rotor. His fuel pressure is at 45 psi when warm. It is adjustable so should he change it to something else. Thanks

 

That rail pressure should be O.K. unless it has aftermarket (larger) injectors.

Maybe a vacuum reading at idle would be helpful. While you have the gauge handy, you might also want to take a look at the vacuum to the MAP and he MAP output voltage.

EDIT: It may also help to know the TPS voltage at the closed throttle position.

 

Changed spark plugs and it made no difference. I will look into those things.

 

when were all these mods done and when did the problems start