http://www.partscats.info/audi/en/?i...234567890&hg=2
Maybe in-tank pumps or pipes?.
I haven't looked inside the A8 but other older Audis had a saddle-shaped tank due to the rear diff in the middle and 4 plastic corrugated pipes to the corners to an octopus-like pump in the middle which sat in a chamber/sump that was kept full. If you look at #27 on the parts list looks similar but internal pipes are not shown.