Is the bike throwing any codes? Check that first, which may give you a hint. This syndrome sounds familiar to me, which is part of what I went through for over a year with my '07. It started with intermittent misfiring that would occur only at very light throttle, then go away for weeks or months--then starting last summer irregular idle right after starting, usually high (1500-2000 rpm), which was also intermittent. It was not throwing any codes until much later in the ordeal.

I changed the IAC last summer and that didn't help the idle issues much if any, but the misfiring kept returning at unpredictable intervals. At that time I thought the misfiring and idle problems were two separate issues, which turned out not to be the case. Last June I did find a leak inside the tank at the fuel-pressure regulator and I changed all hoses, the regulator, and filter. That didn't help, but the culprit in my case turned out to be the TPS. In the last two weeks of the ordeal (June) it was misfiring badly, idling weird, and was throwing P0122 (TP sensor open/low) on a regular basis, at which time I changed the TPS. That was three months ago and the bike hasn't even burped since then.

So, in the absence of any codes, here's my list of most-likely suspects:

1. TPS
2. IAC motor
3. In-tank fuel leak
4. Intake seal leak. Test by spraying carb cleaner or WD-40 around head-intake area while idling. If leaking the idle speed will change, assuming you can get it to idle.

Other ideas:

5. Bad injector or wiring.
6. Bad plug wire

 

Turned out to be a bad fuel pressure regulator inside the gas tank. Thanks for the replies.

 

and check to see if the ceramic insulator has slide over the electrode tip.

 

yep...had the same thing happen to mine... ran like crap. HD warranty covered it

 

Was it leaking around the regulator's seal? That was happening on my '07 but it wasn't causing the aforementioned problems.