Octane alone, will not make your car run better, if it is designed to run on regular at stock advance setting. Purity of fuel can be an issue. Ford does recommend 91 for SVT's. The more advance you run, the more air/fuel you can get into cyclinder. Low octane burns so fast, you use less advance, so it doesn't ignite before you get TDC. Since higher octane takes more time to ignite, you can sneek more in before it lights up. But if you use higher octane than engine was designed for, it means some raw, unburnt fuel is going to sit around the combustion chamber or be pushed out exhuast..Race fuel in a stock engine with stock settings, usually runs worse and worse.
Old trick of adding moth balls to fuel tank was to make fuel burn slower(try lighting a moth ball, they don't burn well at all) Vapor of moth ball cooled air charge- because it burned so slowly, and "raised" octane. Look at a can of octane booster. It doesn't make fuel burn better, it burns more slowly.
Disclaimer: Not responsible for burns caused by trying to light moth balls.