Erratic fuel gauge Audi 80 2.6 B4

[quattro4door]

As per title really, recently purchased a 1995 Audi 80 2.6 and the fuel gauge is very erratic and seems to give a really inaccurate reading. I’ve read about the temp and fuel gauges being a common fault due to the voltage regulator but my temp gauge works perfectly.
The car reads half a tank then within a couple of minutes it’s made it’s way down to just above the red, sometimes it will then climb up a bit a drop again. It also almost always reads as empty when driving at motorway/ dual carriage way speeds then a soon as you drop to 30-40 mph will move up a bit again, really hard to judge how much fuel I actually have at any one time! 🤔

Is there a common and hopefully easy fx? I’ve read there is an adjuster for the fuel gauge on the instrument cluster, would this be a good starting point?

Thanks

[V6Rob]

That to me sounds more like a sender unit fault, but we're dealing with an audi so the only other thing to check would be to remove the cluster, take it apart and clean up the contacts and the tiny pins, found this was the reason my speedo would sometimes work and sometimes not
The little screw is the factory calibration for the fuel gauge so best not to mess with that.