Here's an article concerning the IAC valve. I too am having problems with my IAC valve causing a humming noise in the air intake. I cleaned it with carburetor cleaner and set to let dry. It actually made it worse for me. The humming stopped, but the truck stopped idling high enough to prevent stalling.
This article is from Ford and you can take their word for it, to just buy a new IAC, but they only see it as a short lived solution.
Note: This is for a Crown Vitoria, but the application is the same. Here's the link to the article.