I have been having the same problem, I have a Q Trim exhaust housing w/ a John Craig upgraded stock unit, I think he said it was a t/a 60. The car pulls like hell once it gets going but no matter what I can't get a 60' lower than 2.0 and thats leaving with 12lbs of boost w/ nitto drags. the car runs 13.20s @ 103mph. I can spool this thing up to 20psi and on the brakes, yeah you read it right, it's got to be a problem with my trans or convertor cause I can't brake stall my other gn more than 8psi before it brake the tires loose. Oh yeah I'm running a 2800 stall d5 convertor.