I had a coolant leak from the water pump and during the repair, the dealer noticed that the ECU was slightly out of spec. I was not clear at the time, but I think they made a "repair" by adding a resistor in parallel in the ECU (rather than replace it - which would have cost me ~$1,000!) - and now my FE has dropped from ~45mpg down to ~38mpg.
I have not seen mileage that low in 4+ years. I'm going to confirm that they did this, and ask if it can be reversed.
It is basically negating all my ecomods...