[dmsfrr]

The color of the spark plugs should tell you whether it's running rich or lean, overall.
A quick wipe with a paper towel inside the end of the tailpipe may be similar. Black is too rich, light brown/tan is 'normal'.

Spark knock/pre-ignition/pinging on acceleration can often be reduced or possibly eliminated by retarding the timing a couple degrees at a time until it goes away. Preferably not lower than the factory static timing spec.
Ethanol mixed fuel has a different flash/ignition point that is not the same as 'pure' gasoline.
Backing off the timing a bit can keep them from fighting with each other, creating the pinging.
Using an octane booster may be another possibility?
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