FWIW - I sell hi performance gas (110 Octane Sunoco, $5/gal), and build race motors (for motorcycles).

High octane fuel is only appropriate with very hi compression motors - if you put it into an engine which runs well on 91 Oct pump gas, it won't help anything (maybe slightly lower cyl head temps), and will most probably result in a decrease in power.

Most engines make the most power with the LOWEST octane which will burn clean (no pinging, knocking).

I have won lots of races (literally 100s) running 89oct pump gas in "factory stock" motors.

-David

ps - Yes, any "leaded" gas (low-lead included) will ruin cat converts.