I hear the sound of air moving (kind of a whoosh sound) coming from under the dash on the passenger side. It seems to get a little quieter as the truck warms up.
Maybe a vacuum leak or just the sound coming from under the hood?
It is a 2001, 4x4, 4.0, Auto, Super Cab with a K&N intake and Magnaflow exhaust.
Has anybody ever heard of this?