wildboi013

Ok A 4.0 of course with C&L CAI at certain parts it gives kind of a whistle or squeal is that a bad thing? or?

760Mustang

If you're talking about having your driver's side window down, and there's sort of a hissing sound, that is normal. As opposed to the stock airbox, nothing covers the airfilter. What you are hearing is the intake sucking in the outside air. Just think of it as its way of letting you know it's working.