i have a my04 and i notice that during warm up there is this mechanical pitch noise that lasts for like a sec. I was just wondering what that was?

hard to describe using words but here goes..... phewww for a second but within the second the pitch gets lower.

 

ah.. this was discussed before.. the noise is somewhere around the driver side headlight if i recall.. im not exactly sure what it is... sorry man

 

Air pump.

 

auxiliary air pump, heats up your cat faster so you emit lower emissions.