The change in the fuel filter might be that VW move the filter INSIDE the
tank as a fine mesh screen rather than the filter external of the tank but
before the fuel pump.

Inside of my 88, the tank has a large mesh filter in the center for the
outlet and one on the fuel pump return inside the tank.

This change was might also coincide with the chance in engine size.  The tank
needed to provide more fuel to the larger engine.

Robert