There's a fuse box on the left front fender - did you also pull those?

Only two fuse boxes that I know of. Suggest you repeat the test
procedure except to put the test light in place of each fuse as you
proceed through the fuse population. That will show the drain of a
specific circuit.

There have been instances - generally, not specific to this model (which
I also own) - of the trunk light draining the battery. A simple test
would be to temporarily remove its bulb.

Sandro69,
The test light trick for finding drains on a battery is a great tip for
older cars, but on the new computer controlled cars it can cause
misdiagnosing.  When power is applied to the car, some of the computers will
go through a reset, then 'go to sleep', so to speak.  There is not enough
current through the test light for these computers to reset but they will
try.  Thus, the drain doesn't go away.  Delayed interior lights will do the
same thing.  Now I am not a MB expert, but I have been working on the
electrical system on domestic and Asian cars for many years.  Some cars will
take as much as 15 min to reset and then 'go to sleep', but will never 'go
to sleep' using a test light.  You must use an amp meter on these cars.

Paul
Paul's Auto Electric