The only irritating noise my X6 made was a creak from the centre tunnel/armrest area.
With wiggling it manually, I narrowed the noise down to 2 areas:
1. The silver trim area around the armrest opening button and;
2. the silver trim areas down the sides of the centre tunnel
The solution was simply very small squirts of WD40 into the gaps between the trim and whatever is adjacent to it, I squirted where shown with each arrow, just enough to see the WD40 run outwards but not enough that it dripped down. It sort of disperses out to fill the gap.
I kept cloths to hand but barely needed to wipe anything as I used so little.
The result is I have about 95% less creaking than before. I have to really wiggle everything hard o hear anything whereas before I could hear just when driving along.