There is a cooling down process that begins of the turbo after you shut the car off.It acts similar to a fan.I have owned several non Kia turbo cars that do the same.Lift the hood while this is happening and you can rally hear it.The dealer of one of my cars told me it was absolutely normal.Remember,turbos run very hot (up to 600 degrees F) and they are continually oiled to prevent damage from overheating.Take it to the dealer to confirm!