My understanding is that your motor type size and build and other variables but----most specifically compression ratio will determine the octane rating required to not allow it to detonate. Higher octane does not mean the gas gives you more power. That is a myth. A motor that is set up to run on 85 octane will not make any more power on 110 octane fuel. However, If that same motor had the compression bumped to require 110 octane it would make more power because of the compression increase and would there fore require the 110 fuel. Try to run the 85 octane in the high compression motor and it would obviously make less power/ detonate/ and eventually you would have an expensive day.
Stick with the octane required. Leaded or unleaded does not matter. I would run the same fuel and jet accordingly for it.
If you are at drags, if you love to rejet carbs and are good at it, and if you want just a very small bit more power oxygenated fuel requiring a larger jet size MAY perhaps give you more power. How much, I don't know. Some people just love to tinker...and if that is you...hell than there is nothing wrong with that.
I would say find what works and jet it to run its best and then stick with that fuel and just jet when and if temp or altitude changes require it.
I have some snake oil that with just 2 drops increases HP by about 40% I will sell you.
