I got my 1989 irocs 350 engine rebuilt and decided to go with a stage 2 herbert cam. When I was driving the car back home it shut off at a red light and when I got it back running at every stop light the idle would be everywhere from 2k rpm to all the way down to 600 rpm. I took it back to the shop and they fixed the timing but it still shuts off when I put it in reverse or if im not driving with two legs. Would the problem be the IAC Idle air control? thanks

 

If it was running fine and all of a sudden started to surge you might want to check for vacuum leaks and set the minimum idle speed and then adjust the tps voltage.otherwise it sounds like a computer tuning issue.