ive talked to rolla boy about this before, you should be getting more than 4 psi, on both the 4k ive supercharged with a SC12 i was getting 10-12 psi the the throttlebody after the blower and i get 9-10psi the the throttle body before the blower, the last setup is on a 4k with 40 thou over flat top pistons and not decompressed, only diffrence is they are both EFI and i know thats not the reason, the only other thing is maybe you guys are using bigger cams with too much overlap.