These mustang owners apparently have some sort of limited slip in the rear. There was a clutch pack making the noise. They all thought it was power steering at first. Could the GXP have something similar in the front? (FWD) Anyway, maybe everyone with the problem can pay attention to see if it happens on dry vs wet roads, oh and snowy roads too. I just find this very interesting since the noise has only been around during the summer for me. If you believe there is no way it is anything other than the power steering please let me know.
Also: GXP owners, is this happening while you are moving or sitting still? I cannot reproduce my noise while sitting still.