My ac was fine up until a month or so ago. All of a sudden the air coming through the vents is squealing like a whistle. I have some billet and acrylic billet covers on them, but it only made the blowing noise louder. They have been installed since 03, with one reinstall a year or so ago. I am wondering if this can be anything other than the covers? Maybe the foam on the radio surround vents finally gave up? Anyone else had this start up after years of silence? ,,,,98