I've given that some thought, but I've also been researching the internet trying to find out what the maximum the exhaust gas temperature should run and can't find it. Do you know? I have also thought of just buying a head temperature sensor. Do you think that would give enough feedback to let me know if I was getting any damage? What would be the maximum head temperature? I read one article that recommended both, because they said that after a certain point when leaning the a/f mixture the exhaust gases would begin to cool, but the head temperature would go up and that was a sure sign of detonation. I've already got a water temperature, oil presure, and amp gauge in it and don't know where I'm going to put more gauges.
In my humble opinion, operators of water cooled normally aspirated (non-turbo) engines don't need to worry about going too lean if they pay careful attention to listening for the sounds of detonation (especially at low rpms and high loads).
The knock sensor (if you have one) will help to make sure you aren't doing any damage. Otherwise, the lean burn Honda Civic VX guys would always be complaining about holes/cracks in their pistons and burned valves.
Once you get really lean, power decreases, combustion temps decrease and chance of misfire increases.
Filled up again this morning and mileage was down some even with the increase in the setting on the EFIE, but there was a couple times I forgot to turn it on until I had already driven 3-5 miles, the morning temperatures have dropped off into the 30's the last 2 mornings and we had at least 1 rain day on this fill. This time the numbers were 237.9 miles on 6.246 gallons of gas for a MPG of 38.08. I guess I'm just going to have to play with this thing awhile and see what happens. This is still better than it's been getting most of the time for the last few months.