Loud humming sound coming from air filter box.

Replaced plugs and boots 1st as part of a tune-up. After about 50 miles, had issue with starting and keeping at idle while in park. Replaced IAC valve, worked for about 25 miles. Then comes in this loud humming sound from air filter box that only starts while NOT accelerating. As soon as I start accelerating, goes away. Take my foot off gas, starts up again. Once it starts humming it'll go for about 20-30 seconds before it subsides on its own then repeats after idle range is hit again.