AS ss said. Your compression ratio is the dictator for octane rating of the fuel required. You may need to up the octane to around 98+ and alter the ignition timing back until it stops pinging.
We ran 13 to 1 compression in a stroked BMW using ethanol and wrecked a set of JE pistons .
I may be wrong but i think 10.5 to 1 is the limit for 93 octane fuel.