Originally Posted by Bones
the sound is turbo blowback... ie you are under boost, the engine shifts or you back out of the peddle and the boost in the intake surges backwords through the turbo. Fairly normal with open intakes. The stock intake helps hide this sound. Compressor wheel wear/endshaft play can make the noise louder, but all fixed vain turbos has surge or blow-back noise.
And again, you don't have a blow off valve
You can unplug and/or remove the stock back pressure valve if you would like. But you won't have heat in the winter for 20+ minutes...
What you hear in the video is just at shifting. When I'm on the highway pulling a loaded trailer, the sound shutters, it's leaking air from the same spot that that sound is coming from just not that much.
It never did that last year. So that tells me something is warm and needs to be replaced. What would your guess be?