i have spoken to alot of people today and they have all said it is very common when running high boost or when fitted with a different compressor housing. So i guess it is meant to be, at first i thought it was the sound of wheelspin but then i thought bout iT " I HAVE A QUAIFE DIFF SO THERE SHOULDNT BE ANY WHEELSPIN ) then i realised it was coming from the turbo. it sounds good but i hope it is as i suspect and just the way a turbo sounds when running high boost.