I have been having issues with my 03 450 for a few months now and could not figure it out, so i finally took it to the local yamaha dealer so they could deal with it. It has been popping when ever you hold the throttle in one position but is some what ok under power.They checked everything out valve spec,carb dis assambly,exhaust test etc. all was good. Then they said they pulled the exaust off and re sealed it with silicone and now it runs fine or a lot better than before. I know exaust leaks do a little but will it be this drastic?? They are recomending that i get a new system i am currently runnind a full jardine system.Any thaughts??