I have had problems with this before (actually, I never resolved the issue at all). I am having "flutter" problems with my mini and I cannot achieve more than 18 psi of boost. The MBC responds to lower settings, but once it is adjusted to be above that, (I assume) that something in the charge-air piping is bleeding the pressurized air off.
I have a TurboXS RFL BOV. This is the second new one I have put on the van and I suspect that it is leaking and constantly causes my compressor to surge, especially at part-throttle. I have "shimmed" the spring to hold more boost, but not only does the flutter get worse with the tightened spring, but it still holds no more pressure; 18 psi maximum.
Would mounting the BOV closer to the compressor housing outlet relieve this flutter? As it is, the BOV is positioned right before the TB. I am using a dedicated boost reference line right off of the intake plenum to control the BOV, BTW. Nothing is tee'd into it.
What else should I look for? This is driving me nuts!
Also, I did some VB mods (blocked accumulator and adjusted line pressure) and the trans is doing much better, I just wish I could throw more boost at it at this point, but I think this POS BOV is prohibiting my progress.........
-Les