The bike is an '01 FXSTDI with Stage I mods and Python 3 pipes. This was all done when new. Otherwise it is factory stock. It starts instantly and idles smoothly. The engine has started to "cough" in the intake occasionally when cruising at constant highway speed. It's a true "cough" like an old carb motor running lean, not a missfire. It also has started to backfire in the exhaust pipes during upshifts when I back off on the throttle. The backfire is shotgun loud, only once during the shift. The backfire seems to be worse if I short shift in traffic rather than winding the engine out before shifting. Naturally, this happens primarily in the lower gears. I pulled the plugs (6R12PP) and they were identical front and rear and on the white side rather than any tan color. I replaced the exhaust gaskets at the heads but it didn't help. Any ideas on the cause before I take it to the shop would be helpful. I remember reading something about having to reprogram the EPROM since they seem to forget. Since this is an open loop system without an O2 sensor could it be the source of the problem?