Turbo failure?? please help me

Recently, i am losing boost,gauge shows very low boost about 2-4psi over 4k rpm, I am unsure why. my car starts to lag at about 4k rpm on every gear and then something like back fires with noise and shake. I think that I can hear the turbo is trying to spin but it hesitates (I don't have a BOV installed). when not using the turbo (low rev), car runs smooth as.

any idea, please help, thanks very much.

BOV's come stock, so did you take yours off?

Are you getting any Check Engine Lights?
Did your turbo suddenly get louder or start whinning?
Have you pressure tested your intake for leaks?

im assuming you have a vr4/stealth TT...not a tt conversion? any mods?

sounds like your turbos shot, but normally thats associated with a whine or a screetch. maybe you have a damaged vein? definitely pressure test though

thanks for replys. my 1991 3000gt TT is japanese version, no BOV, engine cheack light not on, pretty much no Mods, just lowered and free boost mod. I will do a preasure test.

How do you not have a BOV...every vr4 came stock with one. LOL. Pressure test, I have a feeling that is where the problem lies.