I have a 2006 Roadliner S with about 14000 miles on it. I have Cobra Exhaust and Poer Commander fuel managment. I got the bike used with about 8k miles and had the same situation. Tried changing to high octane fuel - helped a little. Gas mileage was only around 35-38 mpg. I manually remapped the power Commander to try and reduce peaks in fuel delivery - this helped a lot - gas mileage is now 40-42 mpg. The popping has been reduced but still exists occasionally - usually when I close the throttle during shifting in lower gears. Does this help?