Little bit more of an update; I repaired the MFI thermostat and got it working however the operational distance of the thermostat is about 50% of spec. I have set it up to operate more toward operating temp then at warmup so it tends to run rough during warm-up. The mileage has gone from 16 to 18.5mpg. I am now playing with the rich setting on the injection pump. I don't see why the mileage won't hit 20 and when I replace the thermostat I should see another jump in mileage.
It looks like if I replace the thermostat and then bring the car in for CO, NOx and HC adjustment, the mileage could very well hit 22-25mpg It looks like for the last 3-4 years this car has been tuned with a seized thermostat on the injection pump, so the rich setting has really been skewed.
Leonard

I drive a 63' 220s with a 63' 220seb (M127 MFI ) and an automatic sb tranny. I get 17-20 mpg.