Only for the stock HFC, I'm running Kinetix and they are not needed, although I'm looking into something different potentially. Just not sure yet. Most likely its back pressure...it could be related to pushing too much air or force out at once..it does tend to happen to quite a few people, I wouldnt worry about it. Happens with me too :/

 

Hah, hells yea. Its one engine that you dont get tired of hearing and its pretty unmistakable. I've heard em a few times randomly in a parking lot or on the highway and I start looking around to see where it is...I get some comments from friends riding who dont understand

 

don't worry about the backflow sound -- i can hear it on my stock exhaust (no hfcs, just z-tube & MD spacer).

 

well....my problem now is that it gets kind of raspy at WOT and i want to tone it down a bit. To remedy this, gonna take out the impul V-pipe and put in the MD xyz pipe. Hopefully that will make it better