So I am going through this process right now.
I am at the step where the fusebox has been removed and I am not connecting the wires from branch B1 to the rear of the fusebox.
Here is a photo of my fusebox
It looks as if I have 15 pin connectors as well.
I believe I need to now follow the post 03/07 production instructions even though my E92 M3 is a 2011 (build date 04/10).
The instructions are
Connect branch B1 GN/WS cable to PIN 7 of plug X11001 (the blue colored connector). If Pin 7 is already occupied, disconnect socket contact from branch B1 and with miniature connector M connect to existing cable.
Just looking for clarification as others with newer cars are using Pin 8 on the x11003 (black colored connector)? These instructions say to tap into PIN 7 on the x11001 connector
Also when looking at the Cable B1 from the wiring harness and the x11001 connector Pin 7 both wires are Green/white stripe which match each other in color.
Thanks