You realling need to replace the pipes and air cleaner and add a Power Commander or FuelPak. You will never hear a ping again
I always use the 91 as well. I'm talking about the east coast of Canada. I was on the Cape Breton Trail where the the rule of "when in doubt- gas" applies. The station only carried regular gas and diesel. I don't think he is going to retire early on the .50 cent shooter for my gas tank lol