I need some serious help. I fightered my 2001 Yamaha YZF 600r. I ran the bike for a while without filtering the big air holes in the frame. I also took the exhaust off and ran without that for a few days. (that was like 2 weeks ago) Ive since put the exhuast back on and made filters for the air holes in the frame. But the bike is missfiring like crazy. It started off just miss firing in 5th gear. Now it is doing it in third and fourth gear. It idles fine. ANd first and second gear it runs perfect. But when I get to third and give it gas it does not want to respond. I may have did something to it but not sure. Does anyone have any idea what could be wrong. i'm thinking maybe spark plugs or it may need a retuning but I dont' know?