You cruise on the main jets and set WOT A/F ratio with the PVCR. If you just block the PV off and add more jet, all you did was make it pig fat at a cruise so your not lean at WOT.
This makes total sense to me, now. I ran two 390s, then 2 650s iirc, and although it ran extremely well, and even better with the 650s, it was a little rich. I never blocked off the PV though.