I've got a 2008 yfz450, mostly stock other than I have two Bros full exhaust , kn filter, and I did the exhaust cam mod. I know I need to change my main jet because it is not running right but I went riding the other day and I was hitting the Rev limit and it was petering out and backfiring horribly. Any ideas ? Do I need to mess with the needle jet setting ? I also have the boyssen 2 bowl with an adjustable leak jet ? I'm kind of stuck here. Any help would be great. Thanks guys .