I know this is an older thread, but for what it's worth DynoPort pipes are a WORKS pipe designed to pull throughout the RPM range, the owner Rich Daly is obsessive about performance; I run his pipes on everything I own and swear by them. You won't have to work so hard to stay on the pipe with his chambers, but they are designed for a specific displacement range. So if you want performance details for you application, call him directly; they are still in business but do mostly sled stuff now since the quad industry went to 4-stroke. Krank-It pipes are essentially relabled DynoPort pipes, and are equally good. Scott Carey at Krank-It used to build some incredibly nasty 2-strokes, mainly 250R motors back in the day. My Blaster has a Krank-It motor in it, and it really puts out.