Increasing the max RPM will only increase your top speed, and your peak speed in each gear, which is handy for autocrossing or roadracing. But for max acceleration, upshifting around 4800-5000 is optimum, due to the limitation of indirect injection burn rates... they just don't make a lot of power past 5k or so. Look at the Finn's SuperTurbo dyno sheets - gobs of power, but above 5k it drops like a rock.