Hey fellas - I've got a 2014 400x that has a fmfQ4 and header, K&N filter with outerwear cover, airbox lid is on. My jetting is Main 160 Pilot 40 with DJ needle clip on 3rd notch. It does have 21" tires with the gearing changed. Not sure if that would effect anything. Bike runs great!!!!! No popping on decel......But in fourth or fifth gear if I hold in the clutch waiting to down shift/idle drop the bike will stall. I have checked of leaks and there is none. I do have one of the gas cap vent thats about 7" with the filter button on top. Vapor lock? Need to change jets? Throttle cable? Clutch on adjusted properly? I did recently install a hydro clutch.