All you guys bulding BMW based Sportsters may find the web site below usefull - it certainly helped me to link up the E36 ECU harness etc to a standard kit car loom.
I know it's all in Russian but - On the page that opens;
Click on BMW
Then the third bullet down which gives 3 more sub bullets - go for the second one down.
A drop down menu should appear - choose your year.
Another drop down - choose your model.
Another dropdown - choose System Wiring Diagrams - and now it's in English - great eh!