Ill see if I can find some info on it. Since I have never seen the motor running, I'm not willing to put my word on the line and say it's good. Off the top of my head I can tell you this. It was purchased from a BMW "tech", he swapped an M3 motor into his car. I was told fluids were changed as they should be and the engine was rebuilt not to long ago. I have never compression checked nor leak down tested it. The ecu and wiring harness I have did not come from that engine, but from the M3 engine he swapped into it. I would refer to the motor as a long block with a few extras. I'll update this once I get around to finding info on the M50.