The moose is loose! The howling your hearing in the intake is called moosing. At certian low load, low rpm conditions the airflow in the intake and to the IAC valve form a resonance and produce that sound. There are two real fixes. One is to buy the Mr. Moose pipe, which replaces the original IAC tube from the intake tubing to the IAC with a bellowed hose, which breakes up the resonance.
Or, the better fix, especially if your car is MTX-75 (stick) equipped, is the throttle hang fix. This gets rid of the moosing, and cures the throttle from haning at one rpm when revved. You really notice this on a stick car, but if you tend to spend up the lift for a shift in an ATX car, you'll notice it too. Either mtx or atx, its an easy fix, buy a copper pipe cap, 1/2 inch, drill a hole in it, and put it in the IAC tubing. Check out the FAQ on the contour.org homepage.
