I have a 2009 yz450f that seems to backfire a lot more then it used to when the bike is engine braking. I checked the exhaust for any leaks and couldn't find any ( is there a good way to do this). Also I put a new piolot jet in the bike. When the bike is in nuetral it very rarly will pop but once the bike is in gear and I let off the throttle and the engine braking kicks in it will start to pop a lot. It is starting to get pretty annoying. Any suggestions would be appreciated.