THIS!Higher octane than the factory recommendation doesn't help your vehicle go any faster. Higher octane gas just requires more compression before combustion than lower octane gas. This is essential if you were to increase the compression ratio of your engine. Adding bolt ons does not do this, and would thus require the same octane as stock. Ultimately, you're forcing your engine to work (slightly) harder to undergo combustion and thus hurting performance (slightly).
Listen to these guys. Stop wasting your money and go back to the factory recommended octane.... or don't. It's your money in the end. We're just trying to help. Otherwise, we wouldn't be debating this with you.
This couldn't be more dead on.