True octane value for adding race or av gas

I have a turbo and hear from many people to add some race or av gas to the tank. Just for good measure. The problem is I hear add 1L, 5L, half tank, etc. Is there a true octane value I should be aiming for? The kits say pump gas, 91. It is the boondocker sidekick and I run lower than 5000' at times depending on how high up the mountain I am.


I would like to have a real number to try and mix to rather than just heresay.