Contour Enthusiasts Group Archives Forums Modifications 3.0L Duratec Moosing/ TH Fix- Loss of power? (pics)

It is caused by a resonance and I think it has to do with the spring rate on the IAC plunger valve. If a pulsation begins then it will vibrate back and forth from the waves in the air.
I would recommend a baffle of some sort, not a tube. A long tube looks really ugly but a baffle could be inserted inside the tube. Sort of like a "Tornado" mod does on the intake. I've never been a fan of the copper plug because of greatly reduced airflow.
You could make one out of sheet metal to insert into the tube.