Motorcycle Repair: backfire, spark plug wires, hd sportster

Question
I own a 2002 HD sportster 883c.  In 2003 I had Vance & Hines straightshots & a Hypercharger put on it by a local dealer. New jet kit,ignition coil & spark plug wires were also done at the same time. Had no problems at all. In 2004 ,I had  a seegercycles chopper kit put on it along with a few other pieces of chrome. The bike only has about 5500 miles on it & has been serviced by the same dealer on regular intervals per the owners manual. Late last riding season & this year. It spits & sputters, backfires,shooting flames out the exhaust pipes. This happens after it's been sitting (cold) after a couple miles the bike runs fine! This spring i brought it to another mechanic. He found " coffee grounds "in the carb and said part of it looked burnt. He cleaned the carb and gave the bike back to me ( i was going on a ride that weekend ) Ran fine on the ride but after sitting awhile, was backfiring again as i left for home. Any suggestions ? thanx   Joe

Answer
First thing I would do it check the intake manifold and see if you have a leak. That would cause your problem. A way to check it is, start the bike and carefully spray some carb cleaner around the intake manifold where it attaches to the heads. If the RPMs go up then you have a leak.
If this doesnt solve the problem let me know.
Good luck and happy riding
Mike