190E 2,3L (2.0l original) not run smothly and black smoke out tailpipe

[Shibbeys]

Hi. im from norway and not so good in english but i try anyways.

I have this 1991mod 190E 2.0L, 4years ago it started to run bad, and smoking black out tailpipe and i couldnt fint out what it was.

so i bought a w124.CE-2,3L and drove it to my garage. this car runned good and no problems.

i swaped everything (ecu,sensors,ignition,etc) over to my 190E and the same problems still there.

i dont know where to start figuring out whats the problem is.
i have tested the engine harness and it seems ok.
fuel pressure from fuelpump is ok.
this is a manual gearbox car.

il be gratefull for all answers!