noise then boost drops

[Quicksilvergsx]

I've been having a problem where I am unable to hold boost. I am able to get up to a set boost then the boost will drop when I hear a noise around 3000 -3500. I think that it only makes the noise when the wheels are in motion.

 

[Quicksilvergsx]

The noise sounds like an exhaust rattle, however i went under my car today and found that it seems to be coming from close to the transfer case. Have transfer cases been known to make that sound? I can't see the transfer case or really a rattle making the boost drop though.
By the way, i have no boost leaks

 

[larsenracing]

even if its an exhaust leak and behind the turbo it shouldnt drop it should actually get there quicker. could your turbo be shot. Check for shaft play maby this compressor is rubbing the housing at high boost. also what turbo are you running and what kind of boost. the stock t-to-small (T-28) is only good for 13PSI reliably higher will kill it fast. Also another possabliity for the noise check your flex joint in the downpipe is that in good shape of is it shredding or fraying. Good luck.