at this point there isnt a ton of stuff to really check
Only thing i would do is verify that the back pressure sensor is working right check key on engine off should be atmospheric pressure
The gate may have too soft of springs in it, or the regulator needs to be adjusted so it opens only on the top end. What you might do is go with the heaviest springs and then try to crack the gate open at roughly 75 absolute back pressure but untill then keep it closed.
Check vgt duty cycle, im assuming its going to 7% where it should.
The gate being the the downpipe only needs to vent off the peak back pressure, I think part of the problem is by the time the truck starts to make boost you are already backing the back pressure down instead of holding it a little higher and allowing the vanes to open in the turbo and drive the atmospheric turbo..
My last thing is the cam, i dont know how these turbos respond to a cam. And i also don't know if this cam is designed to help generate back pressure? I think before we get too far into the cam we spend some extra time on the gating.
When does the back pressure get high 3000+ rpm?
