Playing with it is what I do as well.
Even if it’s already really close just for something to do on it.
I’m just a bit rich on WOT, so I’ll be playing with that before long.
If you have a way of seeing the A/F ratio you can get down to the wire with it, but even then what the motor wants sometimes varies from what the gauge says is perfect.
Just a FYI, I was getting right at 17mpg in my Dart after tuning and tuning again.
When getting that specific about it everything matters right down to your timing, including you vacuum advance .
