2008 buell lightening cityx xbsx with jardine gp1 exhaust is backfiring on idle

[CRSole]

There is a very convenient 1/8 male pipe plug in the base of the fuel pump assembly for that
left side of bike, bottom of frame, just in front of swingarm. You'll see the 4 bolt flange and fuel pump wires. The plug is the off-set one.
But I imagine you put fresh fuel in during the 200 mile ride? Seafoam and such is nonsense (IMO).

Nope, I have not ridden this bike at all yet. Just started it up at the dealer and then started it once after trailering it 200 miles in the covered snowmobile trailer (shutoff after a few seconds of running rough), rolled into 55F garage, put on battery tender overnight and started it the next day.

I do know where that fuel pump is because I actually watched a youtube video on fuel pump replacement on this bike during my youtube search for similar setups with these problems. Didn't know about the fuel drain...nice thanks! These bikes really do have some pretty unique design features!