Hi Losadel.
That octane boosters are Bull$hit.
I have tried them in the past on my other ride that also has a ping when it becomes very hot and I drive it hard.
(Volkswagen citi golf CTI)
It did'nt help at all.

I may be wrong but I think your cylinder head is skimmed past max.
If you decide to replace head gasket with a thicker one, cc each chamber on your cylinder head to see if they are all more or less same cc's.