My treasured 105,000 miles 2004 Mercedes CL600 had a major service recently at a Mercedes authorised garage, including the replacement of all 24 spark plugs per servicing schedule. On driving away, I immediately heard a whining or whistling noise from the engine area, which was apparent particularly as speed picked up and dropped off. The garage subsequently carried out several checks in the workshop and road-tested, advised that there was no connection between the noise and their servicing work, and made a tentative diagnosis of turbo wear. Further extensive and obviously expensive checks would be required, they say, to refine the diagnosis. Whilst I respect the skills and the integrity of the staff, it seemed to me that it was a terribly long arm of coincidence that this noise (which now seems to be a permanent feature) had arisen immediately on collection of the car after the service, but was allegedly unrelated. Do you have any ideas or suggestions please?