If it's truely a "ping".. that is a flame front that's hitting the piston face too soon.. it's called detonation. You have to reduce timing, increase octane, or speed up the piston. One of the three.. or some balance of the three will solve the issue.
I suspect that if you ran a *full tank* of 93 octane and are still seeing this.. your not actually detonating.
Some other things that sound similar.. loose spark plug, exhaust leak, an excessively loud injector, or a bent valve.