Yeah had the same problem, persisted with cleaning the IAC unit several times. Each time it worked for a short while and then high idle would return.

Bought a replacement unit from the US some time ago on Stix's suggestion and I decided to fit it last week. Problem gone.

Now I don't know what fucks up on them cause they seem a sturdy unit, and that's why I persisted so long with the old one.

But seems to have fixed it at the moment. I reckon the head breathers venting into the throttle body wouldn't help much.

But others I have spoken to in the tuning trade reckon there is not much that can go wrong with them as they are a fairly basic unit (IAC's in general not just for Harley).

Is there a way you can test it (now its off the bike) to see if there is some sort of voltage drop in the unit??

I dunno but a fuckin PITA if I gotta replace it every 10,000 km, I suppose I just treat it as a serviceable item like oil filters and such.