i have heard alot of silvias and stuff that get this loud psshshshshshshshshs sound when they let off. is it just the type of bov or is it something else.

 

If you're hearing a stuttering sound, it's probably due to the BOV not releasing quickly enough (or lack there of). The compressed air is forced back onto the turbo when the throttle body is closed during a shift. This is also known as compressor surge and it's generally a bad thing.

Besides slowing the speed of the turbines, the sudden impact of the charged air with dramatically shorten the life of the turbo's internal components.

 

This usually happens when the spring is to tight and it can't work properly so it bounces back and forth. So depending on the bov you need a lighter spring or new bov. This is just from the experience I have had.