My friend who has been working on MB's for over 35 years has the car now and we're planning our strategy. The threads on the injection ports were different from the pressure gauge fitting that he had so we aborted the 1st step compression step. Instead he took out all of the injectors and found the following: From front to back, the 1, 2, and 3 injector ends were black and greasy as might be expected. The 4, 5, and 6 injector ends were in varying degrees (steam?) clean with some rust up the collar to where the treads begin. At this point, still don't know if it's a cracked head or merely the head gasket so looks like he'll remove the head next. I will go back and photograph the injectors and each step of this process for further reporting.