Car is a 99 GT, bone stock except flowmasters. My trouble is when I have the IAC plugged in it idles at about 2800-3000rpm, and the Service engine light is not on. But when I unplug the IAC it idles about 700rpm, and will cut off everyonce in awhile and the service engine light comes on with it unplugged I have replaced the IAC, MAF, and the TPS. Nothing seems to fix the problem. Does it need to go to the shop or do you guys have any other advice?