Advanced timing and pinging

As the weather has gotten warmer, my :queen: has been complaining of pinging on the red 94 NA. It runs great, until warming up to normal operating temps, at which point it pings like crazy, especially with the AC on. Running premium and adding octane booster helped marginally, so I suspected a timing issue.

Put the timing light on and found two timing marks on the crank pulley. According to miata.net, one of them is supposed to be at 10 degrees BTDC and the other mark at TDC. Somewhere in the past, a previous owner had advanced the timing for the supposed horsepower boost, the notch that's supposed to be at TDC had been advanced to 14 degrees BTDC. The notch that's supposed to be at 10 was completely off the marker. It looks like it had been advanced way too much.

I set it back to the stock setting of 10 degrees BTDC and then took it back up to about 12 and left it there. So far since then there's been no knock or pinging::Banana:: on regular gas.