Its an interesting post but for me I ran out at half a tank before I changed the pump but after the battery/ alternator died. Though it could be pump died in the first instance, then when replaced it did not seat/ seal perfectly and its sucking up air.
Currently plan is to circle locally burning off fuel to see what happens, good news is an S8 on short journeys can be quite thirsty so it should not take long
Luckily the car is a "Hybrid" as its got LPG so I can swap over to get me home when it happens, also with a Jerry Can in the boot I also consider it a Range Extender.