Seat upgrade wiring help

[Space_coyote]

Hi, looking for some help from the brains trust please. I have a Dec’99 Z3 and trying to upgrade from standard to sport seats. My car has four separate plugs on the seat loom (passenger side) and the sport seat has the single yellow plug. I’ve also got the connector loom from BMW for pre-facelift to post-facelift cars, part number 61106916218. Problem is that there’s one plug on my car loom that doesn’t match any of the plugs on the BMW connector loom. Pics below of my car’s plugs, and the connector plugs. The yellow one in the second pic is the problem child, and from what I can see of the wiring on my existing seat this plug is for the seatbelt pre-tensioner.

for reference if helpful, my car has seatbelt pre-tensioners, and passenger side occupancy sensor for airbags, but doesn’t have seat heating.

Am I missing an additional connector loom or something?

 

[Space_coyote]

Update: I got around the problem by taking the seatbelt pre-tensioner cable with plug from the old seat and using it on the new seat. So everything worked out fine. Still curious though if anyone knows whether there’s another adapter to go from my car’s round/yellow plug to one of the unused plugs in the BMW connector loom.

 

[Fender2004]

I’m sure many members have mentioned putting additional wiring in when going from one seat to another. I haven’t done it myself so hopefully someone else will advise.