Rob R. To be honest with you, the A/C on our cars are rediculously power robbing units. It's your A/C compressor cycling more than likely. Your IMRC doesn't kick in till around 4k, and it isn't really, really noticible like that till you are alomost at WOT, at which point, your A/C compressor is automaticaly shut down till you get out of WOT. Don't worry about it, that's normal and not your IMRC... the A/C thing kills me... even worse in stop and go traffic with A/C on! Good milage by the way.