There can be other problems besides the tranny. Sounds more like the IAT is either dirty or history. This little jewel adjusts the idle. Look on the throttle body, it has wires running to it. unplug it, remove it from the motor, clean it with throttle body spray cleaner. The pintle inside of it should move freely. You can not make it move in and out but it should be clean and free. Inspect the holes that are in the throttle body, if they are cruded up, remove the throttle body- DO NOT CLEAN IT ON THE MOTOR. Once you have it off, clean the blades and bypass passages with the spray cleaner. reassemble. Probably will cure the problem, if not , post here again.