is this the air filter that can cause humming?
http://www.geocities.com/jimmah110/cap.JPG

click here to veiw (http://www.geocities.com/jimmah110/cap.JPG)

I think you're referring to the IAC, or idle air control valve. That black cap goes on a larger silver cylinder held on with 2 bolts and with a harness. And yes, the IAC is what can cause the loud engine humming and other problems.

I don't need a loan for now:D