I took my fiesta 2013 into ford due to a wind/whistle sound inside the cabin when window open, if flow control is set to flow to floor then no sound but aim flow to window and you get a high pitch whistle.

Ford had car all day and come back with no problem found and 2 others models of this age/mileage had the same sound????

Can't believe no one else has heard this and ford not sorting the problem.

Also whilst at Ford I said there was a noise from engine bay I never noticed when vehicle was purchased, the guy went straight to the part in the picture, put he's hand over the part and the sound went away, he said this is the way they are built and every model will have a different sound and went on to say some models have a rubber cover over this part to dead the sound.

So not much help overall from Ford on my problems.

What is the part called in this pic because I forgot what he called it?

Fuel pump, seems quite noisy on some cars.

The whistling noise sounds like one of those things some unfortunate people will have to put up with. It's likely just a matter of aerodynamics which was unforseen when the car was designed. If so then I'd suggest you get wind deflectors which should sort you out.