I have the FMF Turbine Core II silencer on my KTM (with stock pipe) and while I can't comment on the power--I'm too slow to notice--I can offer a few other observations. The pipe, factory, fit great and had nice little rubber mounting grommets (not sure if others do or not). However now, 3 years later and a lot of abuse later, it's leaking out of the weld at the back of the silencer. Also, the very end of the silencer is extremely difficult to remove--in fact, since I wasn't sure I was even supposed to, I quit trying when the normal means didn't work to get it out. I noticed this the first time I repacked my silencer. The reason I tried is because there is a little bit of packing, now thoroughly oil-soaked, wrapped around the very end and I couldn't get it out. So I just stopped trying. I am not sure if this is a big deal or not--maybe others with the FMF can tell me? I guess I can't even really say that the silencer was made poorly, because I crash a lot, but next time, I'll be getting the Pro Circuit just for comparison's sake.