Maybe someone has had a similar problem. Relates to 2016, May, SL400 – 8,000 miles on clock. I have had the car for last 4 weeks. Have experienced the following problem yesterday and today. Yesterday, whilst doing a hard acceleration in sport+ mode had a momentary grating sound (I liken it to the sound of an old skiffle washboard) – eased off the accelerator, everything OK. Drove the car rest of the day, no more hard accelerating, everything OK. Today – same thing, but as I came to a halt, seconds after, the car was enveloped in light grey smoke. Smoke quickly went – I switched to comfort mode and carried on without a problem. Spoke to Mercedes, who advised that it may be a stone caught in the brake pads – this could cause the noise and the smoke. My concern is that this has only happened when hard accelerating – not braking and only when in sport+ mode. Any thoughts or suggestions would be much appreciated.