... have a look at fuse #37 ... there is also another interesting thing to see: the missing Pin7 of X275 / X279 ^^
Just to correct my last post:
I now know for sure that lumbar and side bolsters are not controlled by the seat module. Just the electrical adjustment and seat heater are controlled by it. Its in the TIS ... if you have it, search for the seat module. I installed the TIS in German, so posting the PDF would be worthless ...