Chosen Solution

Hello my friends, I own a Golf Mark 2 and I have a problem with the petrol exchange. The parts I changed did not solve the problem When the tank is full its go only 400 KM or less 20L of fuel only go 140 KM or 150KM max My engine is 1.8 8V ABS Carburettor wires for 1.4 8V My computer in the picture 1: spark plugs 2: coolant temperature sensor 3: internal fuel pump 4: sensor oxygen 5 : computer 6: I check if i have problems in mu computer no problems What can i do with this problem ?

I don’t know but I think the clutch is going out our the transmission?