As far as performance vs octane- VP racing gas has some great information on their web site. The bottom line one shoe does not fit all. You want the fuel to give up its energy at the most advantage point in the piston stroke. Often time high octane can burn longer and actually cause an engine to run hotter as the fuel energy is not optimized. Years ago, I believe it was HOT ROD magazine performed dyno pulls on basically stock, low compression v-8 and the lower octane 87 made more hp than 93 octane or even racing gas. It is important to note that there must be a high enough octane rating to prevent pre- detonation or pre-ignition ( both can be referred to as spark nock). I agree modern electronic systems can somewhat adjust for various fuels but the best scenario is when the physics are optimized.