And since you went there ....
Higher octane does not boost performance by itself. A fuel's octane rating provides a measurement of a fuel's ability to resist pre-detonation, or what is commonly referred to as "knock". Pre-detonation occurs when the fuel detonates before the spark plugs are given their opportunity to burn the air/fuel mixture in a controlled way. Pre-detonation is violent and harmful to a motor. In older motors where ignition timing was set statically, prolonged periods of knock would permanently damage and could ultimately kill the engine.
A manufacturer designs a motor to run on a certain octane. The major controls for this are compression ratio, ignition timing, and head material (aluminum sheds heat far better than steel). If a manufacturer builds a motor to run on 91 or greater, running your motor on 87 could produce pre-detonation/knock. Modern motors have controls for this and can dynamically adjust timing to light-off the fuel before the detonation occurs, but you shouldn't do that, as the motor is running less efficiently when this happens so you are not getting all available horsepower/torque nor are you getting the best fuel mileage when the motor is in this limp mode.
But an important thing to consider, is that higher octane fuels are harder to burn. They burn slower (and detonate less). This normally means less power and fuel economy, but the extra timing you can run and the extra compression you can get by designing a motor to run on 91+ makes up for the slight reduction in burn rate. However, if you run high-octane fuel in a car that was designed to run on 87, you won't be getting any of the advantage that you'd normally get in a motor designed for high-octane. It will result in you getting LESS horsepower than if you ran 87 octane fuel in that car.
The third-gen Vette only required 87 octane. Running premium in that would be wrong.
