Weird whining noise when car is in ACC from engine bay [video]
 

Maybe fuel pump or the head lights? My head lights hum like that but not as loud.

It;s related to the power for the throttle plate, completely normal

Pop the hood and have a friend work the accelerator while you listen, with the engine off, of course. Put your hand right onto the throttle body. It's rewarding to really understand a mysterious sound.