[JeepSnake]

Yup, Buick & Olds used water injection back in the early '60s on their turbocharged engines in the Buick Special & Olds F-85/Cutlass.

Water/alcohol injection helps build power in several ways. As already mentioned, the cooling and cleaning effects let you run more timing or more compression/boost. Additionally, simply by adding the MASS of the water to the fluid passing through the engine, you create more power. More mass flow rate = more power.

I believe military jets have even used water injection to boost power (B-52 is one in particular I think used it in some models???).

MacGyver - take a look at some Jeep tech boards that cover the 258 and later 4.0; they still fight carbon problems! Standard procedure is to introduce Seafoam cleaner into the intake via the brake booster hose till the engine stalls. Let it sit and soak for 10 minutes, then crank it back up and enjoy the smokescreen for a few minutes! (Yes, I have done it...)