i have a 89 firebird with twin tbi. it was running fine, then the rpm's started to rev and the fall back to normal. i check the computer codes and it said vac. leaks and map sensor could be the problem.. i replaced all vac hose's and paid big bucks for the map sensor.
this didn't seem to work, but i noticed it ran better (almost normal)without the vac. hooked up to the map sensor. the trouble has seem to got worse as i've drove to the point that just to keep it running i have to pump the gas alot. i had a new fuel pump put in a few years ago and really haven't driven it much since then. i think that the computer is getting signals from something else, just dont have a clue what.. any idea what i should do next? i have access to another firebird at a junkyard, so if you can help narrow it down i just might be able to afford the parts...
thanks scott

 

check the IAC

 

 

Idle Air Control valve