[C25A1guy]

On basically a stock engine, you will see, let me think.... close to 0 HP. The reason being is that on a stock engine (what I mean by that means no change to compression or f/i) it will run pump fuel easily. If anything, if you tune on 100 octane on a stock engine, you'll probably make more gains with less money without having to add anything else. Water injection kits are more in terms to aid fuel and octane in applications where the fuel being used is already taken to its kinetic maximum and there's no more alternative to prevent detonation.