C15 acert bxs low boost

So I have a 2005 manufactured in 04 c15 bxs that isn’t building the boost it should. The truck is only building 38 psi. I’ve tried most things I could think of to trouble shoot it so now I’m trying to see what I might’ve missed or other ideas. I’ve inspected the turbos, fins intact, spins freely, no oil, all boots and clamps look tight and intact, waste gate on the small turbo opens with about 30-35 psi which I thought was correct. Air filters are clean, fuel filters are new, fuel pressure is 85 at idle and 95 - 100 at 1800 rpm. New lift pump, new fuel regulator, new boost sensor on the head. I unhooked the exhaust and still had the pressure. From what I’m told I should be seeing 50-60 psi with the tune I have. Any input would be appreciated. It runs and pulls fine just once it gets to 38 psi it feels like it stops pulling.

 

It’s a 475 and the tune it has is supposed to be set at 550