I own a '04 Yfz450 with a full Yoshi tri oval titanium exhaust no mods done other that a K&N intake and an EHS airbox lid (10"x10" is cut open and has an outerwear screen). Everytime I hit the throttle hard to pull a weelie the bike slugs and misfires, when I rev it, it pops and misfires and when I let off the throttle it shoots out flames. the bike doesnt rev more than 3/4 throttle. I am probably running lean but I dont know what I should change, needle on step down? bigger main? bigger pilot? any help would be appreciated.