Adjusting a BOV to this?

To make the adjustment, loosen the 10 mm nut on the top of the valve. Using a 3 mm Allen wrench, rotate the small screw in the center. Loosen it all the way out until you feel no tension on it. That is the maximum looseness possible. With the screw all the way flush with the top of the nut, that is fully tight. Normal adjustment for most cars is right about in the middle. If the valve is too loose you may loose boost pressure. The valve will close slowly and will make a little squeak sound at the end.

If it is too tight, you will hear compressor surge (which is what you are hearing) sound when you let off the throttle. It may sound cool but it will damage your turbo/blower.


FWIW I find the newer alum Procharger valve to be very effective, and it is fully adjustable as well, just not as loud as the aftermarket import style stuff, gReedy, Blitz, HKS etc...
Good Luck...