I have a 2011 Streetglide with the 103 engine. At the time of purchase I installed a Harley Heavy Breather air cleaner, Vance and Hines true duals (which removes converters), and 4in. Rush slip ons with 2" baffles. The Dealer put in the Stage 1 download. I was told a separate fuel management programmer was not needed. I rode this bike with no issues for 1000 miles and returned to the dealer for the 1000 mile service and also converted to harley synthetic oil. I then rode for approx. 500 more miles when the engine started to spit and sputter at idle to 2000 rpm. If I rode it hard it ran great but at cruising or light throttle it would pop and bang and back fire. I called the dealership and they said try SEAFOAM and injector cleaner and run a few tanks of fuel through it and it should clear up. It did not clear up and got increasingly worse to the point that it finally would barely run at idle to 2000 rpm. It also Never set any trouble codes at all. They picked it up on a flat bed trailer and took it to the dealer ship. After they had it for a day I called them and they said "its the darndest thing , we dont know why its running so bad." I flipped out and they said "Ill talk to another tech and call you back" They called me back in 30 minutes and said the plugs were bad. They said they changed them and it runs great. The bike has 1850 miles at this point and has went through a set of plugs ? That seems ridiculous....They did not show me the plugs when I picked it up so I dont know how they looked. It does run good but seems to be a little low on power compared to when brand new. I would appreciate any comments , opinions , or concerns on this. Thank You very much for your time.