The first oil change in my 2010 GT I'd taken to the dealership and had it changed. I got the car back and there was a humming vibration over 59 mph from the steering column. Luckily when I took it back to the dealership to have that looked at a more seasoned "technician" looked at it. There is a plastic fairing on the bottom of the car that you remove to change the filter. One of the screws on it was not tightened and as you got over 50 MPH it would vibrate and send the harmonics right up the column.
John