Just got this in from fleabay:
Maybe tomorrow I'll have time to swap it out with the stock one to see if that helps with the backfiring.
I got the bike fired up two days ago (it was 19*F) and it seemed to idle alright, but still backfired like a SOB when you gave it throttle. I did determine that the backfiring is coming from the tail pipe, and having the choke on seemed to help.
Who knows if this new coil will help, if it doesn't at least I have a spare coil now.