Okay,

So I did my research about BOV and BPV...

What I found is that for my case (running 10-11lb of boost) I really really do not want a BOV for my supercharger kit. It will need to be a BPV.

I know stillen comes with a Boshe one factory, but I have been having little things like fluttering and a bit of lag or jumpiness, if that's even a word. I have looked it up and found that the case would probably be the BPV.

Are there any good known aftermarket BPV's out there? I know BOV is a dime a dozen, but when I try to look up BPV's it just transfers me to BOV's which by no means are the same thing!

The reasoning for not going to a BOV is the following:

BPV vents that unwanted boost under vacuum. That's it. Plain and simple. Basically, any positive pressure in the charge pipe is vented until you open the throttle 70%+

Under high boost the BPV works the same way a BOV does, it blows off the high pressure.

Superchargers build boost by RPM, and RPM only.
You don't want boost unless the engine is under load and the throttle is open!
The BPV vents boost at low engine load, even if the engine RPM is high and the SC is making boost.

Venting the boost you don't want with a Supercharger saves the blower, stops fluttering at low load, high RPM situations, and saves fuel economy and accelerated engine wear (especially on engines that aren't built for boost)

Those above are the main reasons I want a BPV. And a BOV WILL NOT WORK to accomplish this task.