I have a 1988 trans am with 350 tpi when when i first start it it well stall after it warms up it will fluctuate between 600 to 800 rpm and when i turn the ac on it will drop down around 500 rpm i have also replace the block fan switch the fans should turn on at 200 and off at 180 but instead the turn on at 180 and off at 160 i replace throttle body ,new IAC valve, new fuel pump ,,new O2
censer,fuel filter,and check for vacuum leaks .I am at a lost hopefully some body can give me a new direction