:cheers:Today, 6-6-2003, I was at my local Yamaha dealer in sac CA to buy a MJ#162 and a PJ#50. When I was talking to the mechanic about rejetting, he said the factory released a FREE Carb modification for the 2003 wr450f. Apparently they take out the LEAK JET, "see page 4-10 and 4-11 in Yamaha manual," and solder the hole closed on the jet then redrill it with a .013 drill, and I think he said they move the needle jet clip up one grove from the #4 position but don't quote me on this one. The mechanic said this factory fix fixes the FLAT spot inherent in the wr450 response. He also said this is all done without changing the other jets from the factory settings. I just got my wr450 last week and I was very unhappy with the initial performance. The header pipe would glow red while stopped and the backfiring while going down hill was annoying, and the was very hot which is not conducive to riding in CA during the summer i.e. FIRE hazard. Today I replaced the PJ and MJ with a 50 and 162. I also installed a Powernow carb insert; a Promoto exhaust silencer and a zip tie fuel mix screw. I have not yet cut the gray wire or modified the throttle stop. Aww all done, now for the test ride. "Wow" my right calf is not on fire any more, the throttle is not twitchy, and "wow" the header pipe is not red hot. I live in for foothills of CA around 2500 feet for a base line. Next week I am going to get the fix done to my bike and ill report on the findings.