Drove into work today, sound has definitely quietened down to near normal levels after flipping the tailshaft back and setting pinion angle back to factory). Not completely gone, but it has always made this sound.
The thing that annoys me with this one is it isn't just vehicle speed... If it was consistent with speed I would suspect roof rack or something - But it only occurs at speed and under certain throttle conditions... I can just about play a tune with it by adjusting the throttle