hi,

i just change my HKS hi-power to a temporally 2.5"inch exhaust with RESTRICTION ....

and now my boost peak is around 16.5psi..... was about 18psi... stock boost/tune.... sometime i heard a small "wiiiiiiiiiiiiiiiiiiii" when boost begin to down on high rpm..

so do my exhaust is causing it or an exhaust leak.... i dont think i hve boost leak if all

was fine before installing the exhaust...

thx for your answer ;p

 

I think the added backpressure from the smaller diameter exhaust that you put on is not letting the turbo spool to what it used to. Think of a crowded room and everyone trying to get out of the door at the same time, same principle.