Erratic Fuel Guage -
Few things I have found out about my 156 are as follows:
1) My car always seems to take about 20 minutes of driving to read a correct amount of fuel, sometimes I'm driving around with 3/4 of a tank and the light is on.. Seems to sort itself out after 20 mins, see if your only going on short journeys, that could be partly responsible.
2) With the 156 the fuel light is set to come on at around 7 litres.. this could be slightly more or less and varies slightly from 156 to 156, this means if you are only puttin' a tenner in a go at todays fuel prices (getting approx 9.2 litres, ish) your getting 2 litres of pop before the light will be on, couple that with town driving where a 2.0L is not great on petrol and that might be why it's happening.
3) If the above two don't really apply to you, I heard from someone else in the forum (name escapes me now) that putting your fuel in slowly can help with the guage givving you a more accurate reading.
I really hope this helps.
Destiny ... The choices we make, not the chances that we take.