Check all of your connections on the boost side. Your preload pressure on your wastegate needs to be at least in the 22-25 psi
range. On my stock turbo and 38r, I tightened the WG all the way down so that it couldn't open. I didn't have enough injector for it to matter.
2003 Ford Excursion Eddie Bauer 4x4 7.3L Powerstroke Forged
Irate T4 BASB, DIY Tymar, Full Force 180/80's, Adrenaline HPOP, Driven Diesel RR & banjos, Magnaflow TBE, GH tuned Hydra, 05 Harley's w/ HID conversion, Edge Insight CTS2, RiffRaff BRV & coolant filter, 20" Black Moto Metal, Dieselsite boots, JLR valve body, 6.0 trans cooler, ARP's