In the latest DIRT BIKE magazine they have a big gun yz250f bike. They claim that Big Gun only did head mods and put an exhaust on it and now they have a 40 horsepower bike with plenty of bottom end. It basically just added 15% to the powerband. Seems a little hard to believe to me, but if its true I would be interested. The other part they claim is that the compression is actually lower than stock.