look at all the modern mx bikes and how they use real pipes and gnarly port timing to make loads of power on the top end. everyone knows that this is a recipe for a torque-less low end and sick transition with any kind of load, right? they overcome this shortcoming by using a "power valve" to effectively lower the exhaust timing by restricting it at lower throttle settings. now they have loads of torque down low, lightning quick transition and a powerful top end.

reminds me of the exhaust throttles i played around with on boat engines years ago.

dave