My 07 Night Train motor is stock except for V&H Big radius (no baffles) and SE Heavy Breather, and SERT. Very intermittently, once or twice every other day of riding the motor will no longer sound the same when backing-off the throttle; it stops rumbling, or change it's pitch. When symptom is at it's worst it will not idle, and will die without working the throttle. There is a consistent workaround to the problem. I switch the ignition off, and back on and re-fire. Almost always, the problem is gone. Anyone have any thoughts on what this could be, or how I might diagnose.