PiosQ

Ever since I vagged my car, a 2002 B6 1.8T Quattro manual, my fuel gauge has been reading erratically. Sometimes it reads full, other times it reads the correct reading (I keep an eye on my mileage on each fillup), but after a while it returns to full. The modifications I did was change the cluster illumination from needles only to needles and numbers. Any suggestions and assistance would be greatly appreciated. TIA