I am running a brpv in my primary side and not in the secondary. I actually made mine out of a factory power valve and was kind of leary to try it but it actually works awesome. I thought i was going to have to screw with it a lot to make it work smooth throughout the rpm range but i was pleasantly surprised that it basically worked perfect with my guess on spring tension. It no longer leans out up top and never varies more than half a point on the wideband throughout. I am running a blow through setup and I can point you in the right direction if you are too, but..... if you have a roots type deal then I will be absolutely no help to you.