I just got an interesting Lambda ECU core. This is part number 0 280 800 001 and had magic marker marking it for a BMW 320. It was interesting this unit had two circuit boards. That second board looks like it did the O2 sensor conditioning that is now replaced with small hybrid board on all later ECUs. Now I know why the metal frame had two tapped mounting holes not used in all the later units. Those two holes mount that second circuit board.

Anyway it looks like any cores that look like our original will work for my upgrade. Same goes for the idle ECU and most RPM relay cores. There is one RPM relay core with a different foot print on the connector pins that does not work (the light green case and connector with tin plated pins).

I have heard of Volvo and a few other cars that used some parts our car uses but never heard of BMW until now.