My AAC has been playing funny buggers too..has been cleaned..
If it's plugged in,(brown plug,purple is just ac isn't it?) it starts and idles fine, then soon as I drive it and stop, idle will bounce between 1500-2000...
Unplug it and idles (about 900rpm) and runs fine but of course now cold start is no good.. Have been just plugging it back in when cold to start it, which of course is annoying..
So quite obviously an AAC issue..not sure if it's mechanical or electric though..
Also not sure is it worth replacing AAC or just block it off and tune for cold start accordingly, or even considering just putting a switch inline to turn it off and on as needed..
I know it Probably doesn't help you much Rolls..just thought I'd throw it in here..