HI all, well I traded a perfect working KTM for a brand new Yamaha WR450 04 canadian model and it wont run at a steady throttle?? Runs great through the gears, real fast good power everywhere but as soon as i hold a steady throttle it splutters and misses????? Dealer tried exchanging cdi box, changed carb, checked compression, changed jets, leaner/& richer. checked timing, cam timing, did leakdown test, still the problem continues...........I'm ready to trade the thing back in and it has less than sixty miles on it, help aaargh!!!! Oh yeah we did all the exhaust mods too fully plugged, end cap off, total spark arrestor removal.No change at all. happens most at 3rd to half throttle.