[Steve Tinker]

I think there is some misunderstanding regarding the underdrive pulley.

There possibly is a 5hp gain with the reduced parasitic loss, but the gain is @ low to mid range rpm, not max rpm. A good dynamometer chart would show only a slight bump in HP @ 3,000 - 4,500rpm not @ 7,000rpm.
And dyno charts with compensation numbers "built in" for gearbox / transmission losses are pure nonsensical - who wants to prove that a gearbox soaks up 12% or 15% or 20% of the rated engine power output, let alone adding in different daytime barometric pressure, temperature and rolling road calibration changes.