I've had the Dr.D pipe for about 5 rides. I'm happy with it. It is a very real gain, especially the torque. My friend has a stock pipe w/spark arrestor removed, airbox lid off, rejetted, and gytr air filter and I smoke him everywhere. I am not sure about the HMF pipe. I do know that the HMF's dyno reflects a 180 main jet where as the Dr. D doesn't require a rejet. hope that helps.
i just got my dr d in from parts direct for $325 and i like the looks of it and thats bout all i know. im installing it tonight.
i know you said it doesnt require a rejet but would it help to be rejetted??