Viermalvier.de, das Geländewagenportal Forums Marken talk Mercedes Automatik und dünne Luft/hohes Gewicht

(Sorry for the English reply, my German isn't good enough).

Try replacing item #53 (A0005450427). This "druckwandler" adjusts the position of the EGR (AGR). When the part gets weak, it allows the EGR to open too early. Eventually it vents boost and exhaust at all the wrong times. This is easy to test, just borrow one from a good engine. You should also replace or install a vacuum inlet air filter.

...Alan