I had the exact same problem on a 07 Dyna after a rain storm. The engine would not idle down because water got into the pin connector and was shorting out the idle circuit The solution was to take the PCIII pin connection apart,dry it out with electrical contact cleaner and then coat the pin connections with dielectric grease. I also moved the connector up under the fuse box and relocated the PCIII module between the back of the battery and the wire harness under the seat. This also makes it easier to access the module for Map changes.(see photos)

 

+++++1 on this alternate installation of the PCIII and probably also the PCV.
CB

 

Another victim to the wet PCIII connectors right here. Happened Sunday. Couple tablespoons of water came pouring/dripping out. Yanked the PCIII out and works just great now. WTF....it ran fine 3 days before when I rode it. Hadn't been in the rain since several weeks before. Nor had it been washed!

 

I filled all connectors with dielectric grease when I installed the PCIII a couple years ago and haven't had any water intrusion problems yet. Knock on wood.