This has occured twice now. I will be driving my 87 Iroc-z 5.7 TPI for some time say 1-2 hours, just cruisin... I shut off the car and come back about 30min-2 hrs. Start her back up and she won't stay running. As soon as I let off the gas pedal it the RPMs drop fast and it stalls. Any ideas? I have pulled the throttle body and cleaned it. I had the TPS sensor cleaned and was told it was ok. The only mods are: hypertech stage 2 thermomaster chip, 160' hypertech thermostat, hypertech fan switch, borla cat back, shift kit, 3.72 9 bolt gears, and gutted airbox.

 

Hmmm. You might want to follow the IAC adjustment procedure. I'm pretty sure there is a tech article on it. Even if that's not your problem, it is a good place to start and definately can't hurt to try.