1999 Alero with history of throttle wire problems, first too loose, then too tight, fixed that, replaced ignition coil housing a week ago because of hesitation, then because of same hesitation i replaced iac, did reset, turn on it idles up to 3000 rpm. when it finally lowers i can go into drive or reverse but it will rev up at random to 1500 and sometimes stay there for a long time, put it in nuetral and it goes to 3000 again and stays around there for a bit. I found one vacuum leak. The only clue is that if i start the car with the heater off, then turn the heater on, it runs like a normal 99 alero. At the moment i turn the heater/ac off, it goes whacky again. Also if i start it with heater on it won't be right until turned off.