I have what is likely a very easy question to answer. I recently bought my bike and I absolutely love riding it in the Supermoto setup that the previous owner put together. I have dirt wheels/tires and I'm pretty stoked about taking it offroad as well! It's a 2002 XR400 with Stage 3 Hotcams, Mikuni Pumper, and a FMF Titanium 4 slipon pipe. It rides nicely and I love riding it. My only concern is that pipe is WAY too loud for city riding. It's absolutely obnoxious. I tried my google fu and it doesn't look like that particular model from FMF was made to fit an XR400. I believe mine still has the stock header, but I am not sure. See pic below: I am considering buying a FMF Q4 as a replacement and want to make sure it will fit without any significant modification to the exhaust. Do you guys think I should check into re-jetting for a Q4? It runs like a champ right now, even considering my terrible kick-starting technique.