It is my understanding that the ECM controls the bypass valve, so techincally, can't you go in the ECM and change that setting? How do we know that 12.5 is the max the blower can push at a given rpm? (and not the ECM just overwriting it by opening the bypass valve.)
Also, with pushing the redline an extra 500rpm, and if we had control over the bypass vavle, then technically you could get more psi...(granted we would need to know the overdrive ratio to determine how much faster the blower will run with an extra 500rpm of motor rotation)