So I threw a 2005 450R silencer (just the muffler, not header) on my 450X. The bike turns over right away, seems to run well once warmed up, but there's lots of backfiring/popping on decel and some while holding the throttle at constant speed (although I'm riding on pretty rough terrain and that could be due to decel as a result of less than steady throttle application).
The airbox is open up top with a Twinair filter. Jetting, from what I last remember, is the NCVS needle, 165 (?) main, 48 pilot, Flexjet fuel screw (turned something crazy like 3.5 turns out...but it's the sweet spot I found after putting the pipe on). Merge spring too.
I would assume that I'm running a touch on the lean side. Is this something I can correct with the fuel screw or should the pilot be changed as well?