Oh man, hats off to you for keeping at it with an automatic. I once tried with a '91 Coroda (auto) and couldn't ever get beyond about 25 mpg/tank. My earlier but otherwise identical '92 Coroda (manual) regularly got over 36 mpg without even trying or ever tuning it. I tried all kinds of tuneups on the '91 including the whole ignition system, O2 sensor, higher thermostat, exhaust, tires, brakes, etc. I finally gave up and dumped it. I currently do much better in my '97 Pissant that's much heavier and has a 55% bigger engine. I chalked it up to "I just can't figure out how to drive automatics."
Keep at it. I'm sure if you perfect it, there'll be a whole lot of people who would like to learn your secret.
Reality is merely an illusion, albeit a very persistent one. - Albert Einstein