I believe the 300-series R129s were fitted with the M104. Sounds more like the head gasket, but you would see oil pools on the garage floor (and anywhere else you park).

The only other item I would look at is the front timing cover seal. Common area of leakage.

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2009 ML350 (106K) - Family vehicle
2001 CLK430 Cabriolet (80K) - Wife's car
2005 BMW 645CI (138K) - My daily driver
2016 Mustang (32K) - Daughter's car