$650.00 or less eliminates a new Q or Hall pipe.

Flat track Racing is alot of high RPM, mid to WOT throttle right? I would think the Aaen would be a great choice.

Other options:
Pro-Pro's/Trinity - There is not alot feedback on how these pipe perform that I could find but they are still within budget.
Paul Tuner - Within Budget might not perform as well on the top end as the Aaen pipe. You might like the power delivery better.