No... No.. steam takes room which lessens the amount available for air/fuel. This actually reduces cylinder pressures and thus power. However, the cooling effect tends to offset this, and the other benefits like the ability to add boost, timing, and/or compression more than make up for it. What? Rebuild the engine after using water/meth? I think you are confusing this with 'war time boost' which was basically overboosting the engine to get the hell outta the way. Had nothing to do with the injection other than it helped the engine live while overboosting. The injection of water/meth in and of itself did not make the power. Its simple... water/meth injection allows you to run more timing, boost, and/or compression. By itself it does not increase horsepower.