Most people who have modified the exhaust have re-jetted, turned out the air mix screws (3 to 4 turns),removed the snorkle, UNI filter or gone Freak. It's a snowball effect. You have to increase air flow through the entire system. If you stay stock and don't do anything you're ok. If you touch any part of the bike that increases air flow you have to finish the job or she'll run too lean. In my opinion it's all or nothing.
