to elimnate the dash insert,carry out a final control test of the fuel gauge via vag com to check the correct operation of the needle.If ok suggest the tanksender is defective and to be sure a resistance test of the wiring from the sender to the dash insert should confirm,you could also apply a fixed resistance down the signa lwires to check empty,full and half tank readings.If this is a quattro then also consider both senders as most common issues are dry soldered joints at the senders.
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