I have a idle problem on a 1991 z28 with a 5.7. when car is started it idle between 2500- 3300 rpms. tried to ajust the iac, but so far nothing works. iac and the tps sensors are new. there wasn't a problem with idling until intake and runner gaskets were replaced. torx screw in throttle body is all the way minmum.

 

huge vacuum leak... look at power brake hose, plenum gaskets, etc.