Are the correct fuel lines 8mm inner diameter? Are they all the same?
- Fuel tank 1 and 2 to fuel tank selector knob
- selector to pump
- pump to carb

My S3 109FFR seems to have a different diameter coming out of each tank. I've had a look in manuals but couldn't find it. I'm not lazy I would measure, but my car is currently 1800miles away and need a mate to buy the hoses for the weekend

i have used 1/4" or 6.3mm which is a little tight but is a better fit then 8mm or 5/16" which can seem a little loose fitting.
oh i see you are not near your vehicle, sizes should be all the same, i think on mine i had a larger size and smaller size, i.e 6mm and 8mm.
i think 6mm maybe the better one to go for,

thanks kommer!!