hope you respond. It sounds like I have the same issue. Did yours turn out to be the intake after all? Or did it turn out to be something else. I put on a whole new turbo and that damn sound still happens.
So when I let off the go pedal, I get a cross between a cat hissing, and whoosh of air coming from the truck. It lasts for like a second.
I thought maybe I was hearing turbo noise that I couldn't hear before the 4" turbo back exhaust, but then I read it is air coming out of the larger aftermarket intake.
Can anybody confirm that?
It is really loud when shifting into OD/4 under load while pulling my toy hauler.
Sounds similar to this guy's video:
His was the new airbox allowing you to hear what is normal. Yours is probably the same thing, but without more info we can't tell. Turbo's make noise. The freer the intake is, the more you can hear it.