I had the same problem with mine. It turns out I had a vacuum leak? I guess it was sucking in air while not in boost. In boost, my gauge was looking right with air flow ratio 11.7, but the truck felt like it was lagging. It would also surge at a stop. Now that the leak is fixed, it doesn't surge and the boost is so responsive now.
I don't know if this helps, but it sure helped mine.
12 Sec. Club! SOLD
La Viuda negra/ a.k.a. Black Betty
LQ4 6.0L, WCCH HEADS, LEVEL 5 FLT 4L80E TRANS. WITH TRANS BREAK, YANK 3200 STALL, TRICK TURBO, TURBONETICS T-76 TURBO, CUSTOM INTERCOOLED, 68lb INJECTORS, CUSTOM S/D TUNE FROM NELSON PERFORMANCE, COMP CAM 212/214 .557/.559 116+2, SNOW METH. KIT, . ALL INSTALLED AND DYNOED AT NELSON PERFORMANCE: 5**?HP @ 5073rpms and 5**TQ @ 4389rpms AT THE WHEELS WITH 10 PSI OF BOOST. ALL 3/4 TON TRUCK 5435LBS, NOTHING TAKEN OFF, STREET TIRES, AND USUALLY 2 BABY SEATS. WANNA RIDE?
SOLD***