Hi.
Well I make 'em, and so far, I have not heard about anybodies experience. So far, I've sold 5 of them. Pretty soon somebody will get their bike running and talk about it. Seems to be working for me. Even though I've raised the ports, I still have pretty good low end, which you gotta have when you are running a 30 tooth sprocket and live in a hilly area. My guess is that high end power won't be as good, but I haven't done any decent side-by-side tests with other high performance designs, so I can't confirm that. All I can offer is accurate information about how my bike is running. My bike has decent pull starting at about 15 MPH, and It will take me up to 35-38 MPH on the level with a 30 tooth sprocket and a 26" wheel. I have a accurate speedo which I trust. Whenever I get to that engine speed, it stops accelerating. I'm not sure what that RPM is, but it seems pretty damn fast, and I don't really want to rev my engine higher than that, unless I want to rebuild it for the fun of it.
Hopefully that information helps.
-Fred