Not building boost to spring pressure

I have a 6.0 ls lq4 with 317 heads, on3 88mm .96 ar turbo, 44mm wastegate with 14psi spring. I can only get 8psi of boost out of it. I've put a 3 port mac valve an ran it at 100% duty cycle and it will o lt get up to 10psi. I was 5.3 same setup and built the full 14psi. Ever since I went to 6.0 I've had this issue. Too much back pressure? I'm stumped.

This may be a silly question, but do you have the seat in the waste-gate? Sometimes it's overlooked during re-assembling after checks and it'll be bleeding off the exhaust pressure needed to drive the turbine.

Other issues may be partially crimped/collapsed hoses, split hoses, shop rags blocking charge coolers, incorrect throttle linkages/mapping preventing full throttle opening, etc.

It's really difficult to make a suggestion when it worked nd now doesn't seem to - you're going to have to go over everything you've done - and it'll usually turn out to be a "duh" item that you're embassassed about missing, from personal experience.

Are you sure the pressure sensor is accurate? Could you have a boost leak?

Fixed the problem thanks to you guys. Found a major leak on my vacuum block. Reworked the tune a bit since i was tuning to the vacuum leak. Now builds up to 11psi on a short road. If I have a full run it should build the full amount of boost. Thanks guys. Pretty amazing that the thing still ran good with that vacuum leak, it just didn't feel as powerful as it should had and wouldn't build past 10psi.

You were right about the "duh" item haha