I'm with whoever suggested opening the butterflies a little more. I can still remember the old AFV that had the big air valve screw in the middle. Had a Mopar one on a Chev back in the day. That thing REALLY hissed
My experience is the more closed the IAC is the louder the noise, the further open the less noise, so you need to close the throttle to get it to open. It may need to relearn the idle setting after a reset the plate is performed.
