Just picked up a new to me 08' yz450f. No matter what i do with fuel screw i still have popping on decel. I read through the jetting thread but still have a few questions. I was wondering if the stock exhaust could be the cause of this? Seems very choked up with the stock exhaust. Could it be causing this? Also thinking of going to a r&d power pump to avoid seasonal jetting changes. Anyone using one a 450? I used one on my 250f and it made a world of difference.