This GL1100 that I bought the last day of Feb. has a stainless steel aftermarket exhaust system that is causing me grief. It is slightly louder than stock, but not too bad, but it makes a single very loud bang when decelerating with shut throttle from speeds over 60. The air cutoff valves are in good condition and there is very little afterburn at speeds under 60, but I think the air cutoff system cannot handle these pipes. I've tried very rich idle, very lean idle, fast idle, slow idle, retarded timing, putting 6" extensions on the pipe ends, squishing the ends of the extensions, nothing helps. Would it help to put baffles in the back 8" pipes of the mufflers? I noticed they are wide open, but I can see a baffle further forward. I tried killing ignition while in the decel, but when I turn it back on I still get the bang. I'm going to try this more, maybe with some throttle first there won't be a bang and maybe I could rig up a vacuum-actuated switch for this, but it seems so unusual that even I am reluctant. Any advice?