A clogged catalyst can cause a performance loss. Taking it out on the interstate and flogging it as well as holding it to the floor from a dead stop up to a safe mph can help blow / burn the soot out of the catalyst. Some refer to this as an Italian tuneup!

I think it is something stupid like that. I have to check timing next. I did a couple Italian tuneups and it seemed to help a bit. After I plan to check the crossover pipe and see how terrible that looks too.

I checked the transmission fluid and it is CLEAR. What's up with that? Change and filter I think is on the way.

Try blocking off the EGR valve, or at least check its operation. My first MB was a 123.190 (non-turbo wagon, OM617 motor) was an absolute dog with lots of white smoke that smelled of diesel and it could barely go 50 mph. I tried everything I could think of: new filters for air and fuel, set the valves and set them again, replaced all the injectors. Engine ran smoothly with no missing, just miserable power and too much smoke. Finally I blocked off the EGR, and I instantly had a new car. Top speed (only explored once) was an indicated 110 mph. I was SOOO happy! The EGR had failed in the full open position, effectively choking the engine on its own exhaust and cutting off most of the oxygen.

???

CLEAR???

how odd.