Backfiring Problem?
 

If your bike has started backfiring all of a sudden on decelleration, and you just happen to have Vance & Hines baggers on your bike, youll find the the problem is a cracked header pipe at the first bend on the rear cylinder.
A few have been known to crack, and they will replace them under warranty if you have it. Other than that your on your own to repair or replace.
I welded a patch over my cracked pipe and its holding well.