Don't know... but some random thoughts....
1) Does your beeper work? Could it be overheating?
2) Does it feel like it's bouncing off the rev-limiter, or is it trying to die at WOT?
3) Try riding it with the rear hatch off. If you have an exhaust leak... it may be choking it self.
4) When is the last time you cleaned the RAVE valves? If they are stuck open, you may be loosing torque.