I have a 2005 Fatboy which used to run pretty good. Now the bike starts & runs up to 50 mph or so and then seems to bog down and not pull anymore....as if it goes down to one cylinder. No throttle response at that speed and impossible to pass anybody. We changed out the gas and all fuel line filters and still persists. Next changed out plugs, plug wires, coil, power commander, battery & cables and still no better. Dosen't seem to be mechanical or fuel related, but we have not been able to fix the problem. The computer says it's misfiring, but that leaves lots of doors open. Any suggestions/help would be most appreciated.