ok, new to me 1994 fatboy with thunderheader (91 ci), screaming eagle ignition, hi perf cam and S&S carb and certified 13900 mi. sounds like a howitzer every half second at idle. problem is a blip at 65 to 70 mph. the engine seems to misfire on one or the other cylinders, just once or twice and only at those speeds. previous owner thought it may be fuel contamination so it was all replaced, even the fatbob tank for a new OEM. problem still exists. wondering if it is an ignition issue or a mixture issue? thoughts anyone? Thanks.