I had the problem on a trip to California last fall and it continues. When ambient temp is above 104 F my 2000 320 ML went into limp home mode and decelerated fast. Moving the shift lever into neutral and gassing it confirmed engine fuel supply, returning to Drive, it picked back up like normal. As the temp went higher (up to 109 near Yuma) the problem repeated more often. Stopped in San Diego at MB dealer. Absolutely No codes! worked with team of 4 there and the MB world database on problem. Concensus was probable mechanical, heat related fault in Transmission Conductor Plate.

After replacing TCP, no further problem - until I approached Amarillo TX on the return - ambient temp 104 F; problem repeated.

No further problems until last week when it was 107 in Dallas - had 3 more events until temp dropped below 104 F

Will check out the Fuel Pump approach, Thanks!