mmm, its sounds like you have a similar problem to me. I recently had the cambelt and auxy belt changed on my car and now just before coming on boost i here lick a tapping sound that speeds up with the revs and then you cant here it once the turbo spool is louder. happens in all gears. I suspect it may be linked to when the cambelt was changed and need to go back to the garage.
Did speak with nick about it and he said to check the N75 wasnt catching on owt and also check for a split in the pipes that goto the n75, all is fine though. I cant replicate the noise on tick over and just revving the engine. The car needs to be moving.
So i think theres not an issue with the turbo.