I didn't see this thread until this morning, I immediately thought of that stupid cotter pin that connects the wastegate arm to the flapper. When I put my old 14b in I didn't use both bolts to connect the wastegate to the turbo, and that caused the same issue. IRRC I'm on my 2nd year now with a paper clip holding the arm to the flapper..
BTW, I did a few fulls last night as was reaching 22psi at 3478rpm on my Evo316g/2g manny/o2/28x10.5x3.5/stock 2g head & IM. You've got a leak somewhere, go back and tighten everything up.