Working on my s50/e30 swap I ran into a snag.

I have a harness for a m50vanos engine but I don't know what car it originally came from. I'm trying to identify where each plug/connector goes but most of the wire colors don't correspond to the wiring diagrams I have looked at. I've compared it to wiring diagrams for 95 and earlier 3 and 5 series cars.

Is there any way to narrow down which model the harness came from?