I wanted to share a solution to a problem I had on a 2002 FLHTCUI (27k miles). The bike had poor low speed performance at light throttle settings, rough idle, backfiring (the true definition). It ran decent under acceleration. It also had a rather nasty noise coming from the lower end area. An early Twin Cam with close to 30k on it, I figured bad cams, cam bearings, tappet roller(s) tensioners, etc. After reading the forum, it sounded like a vacuum leak, leaky internal fuel line might be the cause of the missfiring. I figured I better look into the engine noise first or a missfire would be the least of my worries. I pulled the cam cover and the tensioners were due, so I pulled the cams etc. The cams, cam bearings, tappet rollers all looked great. I put a wrench on the flat portion of the crankshaft and turned the engine a ways. It did not turn very smoothly at all. It had a notchiness (is that a real word :s) to it also. This got me thinking that it was like the rotor magnets were being felt. I pulled the primary and the compensationg sprocket was quite loose. I pulled the rest of the primary drive parts and checked the stator and rotor for physical damage. They looked just fine. I ohm checked the stator for good measure and it checked good, so I buttoned everything up and noted that the crank now turned smoothly. I finished up the tensioner job and started the bike to check for vacuum leaks etc. It idled perfect. I test drove it and it ran great ! The noise was gone too. Apparently the loose compensating sprocket and or rotor being loose was causing some kind of disturbance to the bikes fuel injection system (Delphi). Maybe someone more familiar with fuel injection can explain why.