Man, I can't imagine that much humidity now except when it is raining here
I'm glad you have tried leaner AFR also
The moisture in the air does turn to steam inside the combustion chambers, correct
Water molecules in real humid air displace the oxygen molecules in it making it real hard to make big power when it is humid, no matter what the outside air temps. are, altitude is or barometric pressures are
I'm not sure that all wide ban systems read exactly the same either, just like tire pressure gauges do
