on my 04 HD ultra classic, the check engine light go´s on and off, more then off. also i removed the baffles from my VH mufflers so i could listen to it better (wear Hearing Aids) and discovered it was missing and cutting out from the forward cyl. as long as i kept a high RPM it smothed out but the minute i let it idle down slow or fast it would miss in large volumes plus pop back like back fireing. The plugs have about 6000 miles on them, my mechanic change the air sensor wiring harness and the light went away for about 200 - 300 miles and then started blinking on and off sparatecly! gas mileage sucks; i do have a side car also which cause´s more drag but still i should get better then 130 barely miles to the tank!!!! THANK YOU LOOK FORWARD TO YOUR REPLY