octane Boost
 

What is the best over the counter Octane Booster?

for what intended use?

Klotz makes a great "race gas concentrate".
Cheapest way to get high octane fuel is to buy high octane fuel, not to mix your own. Buy it in 55gallon drums.

Run 2 tanks in your boat. Electric switching solenoid to swap tanks. Wire the "regular" fuel tank to a 4 degree ignition retard module.

Switch tanks and give it fifteen seconds to complete the swapover (5 seconds with injection) and then you can hammer it.