Hi, you're on the correct tracks with your thought process!
Check this out for the part numbers/diagrams (easiest way for me to refer to them):
https://www.realoem.com/bmw/enUS/showparts?id=DU52-EUR-09-2006-E86-BMW-Z4_30si&diagId=51_6103
To remove the side pieces, you need to:
- remove part 2 (the fabric B-pillar cover) - this is just plastic clipped in. They are strong though, and this part is
hard to find second hand, so be careful and take your time prying it loose
- remove the trim piece 4 which is now unblocked by the B-pillar trim (this might have a plastic push rivet at the front, by the door shut)
- this will then allow you to remove part number 6 (just unclips)
- you will then see the plastic pin holding the carpet in, which is hidden under trim pieces 4/6
- there are more plastic pins holding the carpet in near the rear lights - you'll just have to look for these as there's a few and they're hard to describe
Once the side panel is removed, you can then tackle the back/bulkhead panel:
- remove the small boot carpet over the battery, and you'll probably see a couple of plastic clips holding down the floor carpet. Remove those
- remove the plastic push clips from the side of the rear bulkhead carpet (if not already removed when tackling the side carpet)
- the carpet is then just push-fit into the bottom of the parcel shelf assembly.
Be aware - the side carpet has some hooks which hook into holes on the bulkhead carpet, so don't just pull it out backwards, but make sure to work it out safely. You can see the hook (there's 2 per side, I think) on the right of photo 2 here:
https://omegaspareparts.com/product...1SoWTUHaNnatxoW4P7m53GaOscyLiU6nd6nV13_kmKZE-
Now is a good time to consider rear shock replacement too, as you have to do this job to remove the carpet to expose the nuts to replace them...
That should be accurate - it's from when I had to refit the boot carpets in my car, after it was stripped out by the previous owner for track use, so there might be a few clips I missed out when rebuilding mine