If you have a volt meter that reads duty cycle, we could settle this discussion. Maybe Pat or Dave could chime in here. Guys where is your duty cycle set? Would you mind terribly leaning it slightly to see which way the duty cycle readings go? You gents might discover why your cars are running so poorly. A fixed reading indicates a problem. Have you guys pulled the resistor (R16?) out of the wire harness to advance the timing???? It makes does make a slight difference on these 16V motors.
BTW wifes 87 16V auto usaully runs right around 20mpg. With a 5 speed I would expect a bit more.