1989 IROC, 305 H.O., 700r tranny, TPI, 124,000 miles....just bought the car 2 months ago...started messsing up when trying to pass on interstate, after passing gear would "kick-in" the car would hesitate until I backed out of it...then it started dying when I would come to a stop...now it will not even idle, it cranks and then dies...??I can however force it to idle if I turn the a/c on??,but when I put it in drive it dies...if the a/c is off I cannot force it to idle..

 

Start with the basics, like clean plugs, reliable plug wires, a good cap and rotor, clean throttle body and IAC, properly adjusted TPS and minimum air, good vacuum hoses, leakproof intake ductwork behind the MAF, a clean and functioning PCV valve, and correct timing. Once the basics are covered, you can diagnose the problem without fear of complications from these "wildcards".

Testing fuel pressure would be a good start. Low pressure will cause poor idle, hard starting, and lack of power production. Since the MAF is essentially ignored until the engine is running, it rarely affects starting, so your symptoms would indicate that the MAF isn't an immediate concern.

 

I'd start with what vader said, especially if you don't know the current state of tune.

After you do that, just remember that the engine only needs three things to operate: Air, fuel, and spark. After you narrow it down to one of the three systems, troubleshooting it is usually pretty straightforward.

Good luck, and have fun