OK so the bike has always lacked a bit of low end power since it was new. It seems I have to clutch a bit if I want to stay in a high gear and there is some hesitation when rolling the throttle on. A few people have claimed that this slip-on exhaust has helped on a lot of the YZ450fs. Thoughts? thanks.
There is nothing wrong with the OEM Yamaha muffler design, so it's unlikely that a slip on would help. Your issue sounds like a carb tuning/jetting issue.