Torque and horsepower do not peak at the same RPM. Horse power is related to torque X RPM. The point about shifting so as to maximize HORSEPOWER delivered is correct. An unmodified NA has a peak HP of 215@5700 and peak torque of 229@3000. Given that peak HP occurs just before redline, you will go fastest if you shift at 6000 RPM (or very close to it).