Just bought a 2003 wr450f which I absolutely love. Anyways, what are the best tires for dirt/grass/mud trails and motocross? What psi I would you recommend to start at? Anyone willing to give a quick explanation of the mods I've been reading about? Throttle stop cut, gray wire etc.? What would be a recommended starting point for jetting a bike being run at approx. 3000'. I noticed the bike wants to back fire every now and then after getting off the gas. Thanks for any help!