My 2011 4/4 has had a sooty exhaust from new. An ECU flash done at 3 years old improved performance but still has sooty exhaust. Unless I really warm the cat up prior to MOT it will fail on the Lambda. Reading shows a lean mixture. HC is usually around 8 with a limit of 200ppm.
Think if you note exhausts on nearly all modern vehicles using unleaded petrol they have a sooty exhaust exhibited (UK). How the Cats survive I have no idea.

4/4 Ivory 4.1:1 axle, Mercedes A200 AMG