It is intermittent. LAst night on drive home I was pushing a bit on a back road with windows down and sunroof open and could hear the noise in 3rd although quieter. It seems to get higher pitched and louder the higher the rev range. However, there is no noise when the car is stationary and revving. When stopped I turned the steering full lock both ways and no change in the noise. I then turned the engine off and started again no noise. After a while of pushing the car the noise came back almost when the turbo discharged in 1st gear - drove for a bit at normal speeds and noise was there. Stopped the car switched off engine and it was gone?