There has been a lot of talk on quiet exhausts lately. While the closed courses I run have neighbors FAR away, there are a few trails nearby homes so a quiet pipe is the only way to keep peace. The battle between low noise and HP continues. First, let me say I wasn't expecting much with this mod, but pleanantly was surprised. I expected a serious lack of power Using a stock YZ pipe, a $1.47 metal 1.5" utility sink drainplug from Home Depot, and a hammer , I popped the sink plug (has many small opening) in the tailpipe. It allows estimated 55-65% flow by visual inspection. First, I decided to run my current jetting for a test run. EKP#4, 170MJ, 48PJ, 100MAJ, untouched AP, YZ timing, '00 WR, WB tapered header--600ft, 70 deg F. I ended up not changing it due to mud buildup. Wanted to change it out to a EKR, and perhaps 165MJ, but didn't want to risk getting crap in the carb. Anyway, the bike ran GREAT! MUCHO quieter, there was no comparison. Yes, the power was a little soft, but it felt like bottom was just as good, it just didn't rev so violently. Didn't foul a plug, or show any signs the jetting was really that bad. That surprised me a little, too! Overall the power wasn't that bad given the conditions. My rear end wasn't sliding out as much due to wheelspin following terrain. Basically was going just as fast as always though this trail. My 'WR was pretty pumped up before, and now it's just a little more tractable. A few times I could swear the bottom was actually better, as evidenced by wheelie ability. It felt like more power than I expected to have when corked the pipe up. I didn't really get a chance to ring the motor up too hard due to conditions. But the delivery was smoother. It felt like WR timing with an open pipe and aggressive needle. James, Taffy hopefully you guys read this. You remember about a month ago I was going to try the new jetting specs you recommended. Well, due to the nasty mud around here this time of year, I want to hold off on wicking the power up until it dries out over the summer. Right now a smoother delivery is what I need. I do wish to hear what your thoughts are on jetting with the modified pipe. Any YZ pipe owners may as well give this a try for either cheap noise reduction or smoother delivery for mud. It's only $1.50, and maybe some leaner jets. Check out your plumbing shop!