I have a lightly modified 05 RoadGlide, it has a set of Andrews cams, Reinhart duels, SE breather, and and a power commander 3. The bike was tuned on the dyno by a respectable shop here in Indy after the cams were added and it ran great, other than that the motor is stock with 60k miles on it. Last year on a 10 day trip to Maine it started to not want to idle when we came to a stop, I could feather it and keep it running but it wanted to die. It seemed ok on the throttle and at speed. I pulled into a NAPA I saw and got a set of spark plugs and it seemed to fix it. Plugs probably only had 3000 miles on them but it seemed to work so off we went. seemed fine then about 2000 miles later it is having same symptoms. I pulled the pluga and they looked fine but I replaced them again anyway and it ran fine. What is causing this? How may miles should you get on a set of plugs? Are coils going bad or something like that?