For what it's worth, even though I'm an Aussie, I own a 2012 XL1200C, and within 4 months of buying it and literally riding it off the showroom floor, my bike started 'surging' and misfiring, at any speed and/or rpm below 110km/h (~70m/h)...Took it to several dealers who didn't know wtf was goin on, after havin several months with the bike, total (each dealer and service dept I gave 2 wks).
Finally, in an act of desperation, I took it to the last HD-related service place. Took them literally 30 mins to find and fix the problem...Apparently, the way certain EVO engines are built, the softails "tend to" have faulty Idle Air Controllers, and if you go over any kind of flaw in the road that is of a 'decent' severity, the IAC can become 'jammed' open, and the bike ends up taking in what amounts to 100% air, AS WELL AS the tuned fuel amount, resulting in what is essentially misfiring, until the bike is 'asked' to start consuming s**tloads of fuel i.e. a 2/3->3/3 open throttle.
Bottom line, SPECIFICALLY ASK to get the IAC checked, REGARDLESS of the model...My old man owns a 2010 Rocker 'C' that has no problem, but he also bought a Breakout (NON-CVO) that also had the same problem, after installing stage-1.
It seems that, as long as the bike is stock, the IAC is ok, but ANY exhaust/airflow modification, causes the IAC to lose it completely.
MAKE SURE TO GET YOUR IAC CHECKED, AFTER YOU INSTALL A COMPLETE STAGE-1 MOD!!!!!!!!!!