if you look at last two samples, one being cyl 1 at about 1,100 rpm, I'm at 3.5 psi at peak as valve closes. Cyl 4 at 1,600 it peaks at over 7 psi, couldnt keep either one running long enough to get rpm to stabilize. I pulled B2S1 O2 out and checked back press... Login to read more.