Like what was said above, free flowing exhaust (head work etc) will lower boost #'s by allowing the cylinders to fill more efficiently leaving less pressure in the intake manifold (where boost is measured). Belt slip isn't going to help either

 

I hope thats the case not that it is running bad, just so that I know, ya know LOL.. It all is prob playing a part here..

John

 

I bet its belts slip. Try some belt dressing just to see if it goes higher. What kind of belt are you running?

 

Goodyear gatorback...

John

 

They have worked the best for me. The gatorbacks seem to have good grip.

 

You know I was having a similar problem before I had my boost gauge in. I notices that when I would rev it up and decel quickly the bypass wouldn't release any air. So I took it off and opened it. It had a thin plastic inside that looked like it had been sucked in and wasn't sealing right. It also looked like it was starting to so wear as if oil had got in and was deteriating the plastic. Well I don't know anything about these things so I just set the plastic back on where it sealed like it was suppose to asembled it back together. Took it for a spin and I hear the "**** ****" sound once again. I've also read that sometimes if you turn them the opposite way and the bypass worked better. So If i were you I would first try and turn it 180deg and see if you see any improvements. If not take it apart and check that thin plastic that's inside make sure there are no holes and that it's setting in there right.