Motorcycle Repair: sputtering/backfire at low RPM, slow jet, highway speeds

Question
I have a 2005 Sportster 1200R which was stored last winter.  After breaking it out in the spring, I noticed it would sputter at lower RPM's (2500 and lower) around 40 MPH or less.  I also noticed it would backfire when down shifting.  I ran several fresh tanks through to get the Stable out and changed the plugs...no help.  Taking it to the dealer, they stated it was 2 bad seals between the exhaust and the engine heads.  These were replaced and it helped a little, but still sputters and backfires.  However, it does run good at highway speeds (3000+ RPM and 55+ MPH).  I also noticed the enrichener knob will now work its way in (closed) while riding down the road..HELP!

Answer
To adjust the inrichner you will see a small platic ring behind the knob. tighten it a little and that will hold it back.
On the sputtering, your slow jet might be slightly plugged with dirt. You need to pull it and check it
Good luck and happy riding
Mike