I am really stumped and hope someone can help. At cold start there is a howling sound coming thru the air intake that after a minute it starts to go away completely. Then as soon as the gas is applied the sound comes back. I have replaced the IAC twice and the last one was with a genuine motorcraft but still same thing. When it's making the sound I can pull the plug on the IAC and it will go away but runs bad. Really stumped on this and would really appreciate any help