I have a ss turbo with a trifecta tune and 3"downpipe. It just started making a a vibrating fart sound(only under boost and when warmed up). Sounds like it is coming from turbo/downpipe. It runs flawlessly when it is cold but starts after about 5-10 minutes of driving. Again, only happens under boost and boost pressure does not seem to be affected much if at all?? I had my local mechanic check for exhaust/downpipe leak and he said it is fine. Is it the turbo? Blow off valve? Anything else?? Thanks in advance. WHere is the blow off valve located? I believe I found the vent for it

 

Don't give it so much gas,
and try some beano..