I'm not sure how it's goverened. If it is governed it's very very likely to be the CDI box. check the pin count and arrangement and search online, an unrestricted replacement should be very inexpensive, like 10-20 range.
Other restrictions may be the cams and valve sizes, exhaust size, or most likely in the carb size. bigger carb and properly jetted will be key to making the kit perform.
it may also be restricted by gearing but if that were the case you'd be doing wheelies.