RE: Speedo Accuracy
If, as you say, the error in the indicated speed and the error in the
odometer are the same (as mine has been on two different vehicles, an '85
and a '90) then there is nothing wrong with your speedometer.  The problem
is with the wheel/tire combination, the tire diameter (and circumference)
are not what VW speced originally.  Theoretically you could change the gears
in the speedo to compensate for this but why? If you know the error you can
always correct to the right numbers if needed.  An error of around 2 to 3%
in such an instrument is well withing the tollerances normally expected of
such equipment for use in the field.