Some ST's make a wind noise from the mirror. The mirror itself may not seal 100% against the door due to a worn gasket. Remove the door panel and there is an access hole/holes to remove the door mirror. Get some foam rubber and push it into the hole and see if that changes anything. I had that issue but Ford didn't sell a gasket for the mirror, so I kinda made one from gasket paper and foam rubber. NOT spray foam!