My 92 mustang 5.0 with a power dyne blower develops an issue with the IAC ones a year where the rpms will go up to 1500 at an idle or after a downshift will stay at 2500 and keeps the engine at that speed while driving. I can accelerate past that rpm but won't drop below that speed. Voltage on the tps is correct and has a new one. If I replace the iac it will be fine until next year but I can't imagine all of the motorcraft iac will go bad that fast. I know they got issues with the cheap ones. Any idea?