I just took my 01 fatboy out for the first time this year. I rode it twice this week and I am noticing a knock on acceleration ONLY which sounds like its coming from the front of the motor. it only happens if I roll onto the throttle anything more than gently. Over the winter I did repaint the bike, so I took the tank and fenders off, but I lock-tited every bolt when I put it back together, so I dont think its got anything to do with that. I am more likely to believe that it would have something to do with the fact that I put on an ultra cycles 2 into 1 pipe that I bought this winter. It does have a baffle in it and I used new exhaust gaskets. It has the stock air setup. When I tightened the flanges back down, the nuts bottomed out against the exhaust ports, which makes me think that it did not make a tight seal and it could possibly be that there is a leak. Also I read a lot about fuel knock being a problem. I put in just under a gallon of the fuel I took out of the tank before I painted, just to get me to the gas station, so it was old gas, but then I filled up with 93. The bike is running great with the new pipe, no backfiring or popping on decel, and it is not sluggish. It is just this knock that concerns me. Any help?