Hi Peter
Have also spent many hours on my wiring! I don't know exactly how similar your DME/EWS is to mine, but I'm still working on how to interface these with the rest of the wiring loom.
I'm going to try using the speed sensor signal from the switch on my rear diff (E36).
Found the crankshaft sensor which might operate the rev counter (?)
Will try tapping into the oil level and oil pressure wires (from the DME Module 3).
Theres only a couple of wires I think I will be using from module 4, the fuel relay and the EWS wire. There is a coolant sensor in there but I'm not going to use this.
I've been trying to simplify all the wiring down as there's absolutely masses of it, mostly too long, will put a pic up.
I will be ready to test it out in a couple of months
so I'll let you know if it works!!
Cheers
Tim