[Jeff Chambers]

Have you datalogged anything with the setup? There are two things that I can think of right off the bat that may affect your power level outside of the mechanical pulley relationship. (1) the computer will only recognize an engine load (volumetric efficiency) of 2.0 which will be reached somewhere around 16 pounds of boost. Unless your tuner has renormalized the load tables you might be peaked in the PCM algorithms. (2) A factor of the first is that once beyond the load limit the computer may be reverting to the Load_with_failed_MAF tables and limiting fuel delivery. Datalog load, fuel delivery, injector pulsewidth/duty cycle and fuel pump duty cycle when you're under max boost to be sure that you're getting the fuel delivery that you think you should. How is your A/F (wideband) as you get near the peak boost?