I have determined the cause of my 2-3 mpg decrease in mileage after a tuneup
and O2 sensor change. The problem had nothing to do with the tuneup or O2
sensor change. The problem was an adjustment I made to the throttle switch
because it was not closing at idle sometimes. After readjusting the switch
to spec, mileage is back up to 17.5 mpg in city driving.

Mark McCulley
87 syncro Westfalia