Ah, found my answer on a version of these instructions for E92/3s (mine are for E90/1s):
If PIN 8 is already occupied, disconnect socket
contact from branch B1 and with miniature
connector M connect to existing cable.
'11.5 M3 sedan | Jerez Black Metallic | 6MT | M Performance Exhaust | no DCT no EDC no NAV no nonsense