methanol injection

I don't agree. Water/meth injection is not used to cool the intake charge, it is used to suppress detonation. If you do not have detonation, the injection system will take power away, by displaceing the oxygen and fuel reaching the cylinders. Water doesn't burn, and meth has less heat(power) content then gasoline. You would have to have a VERY high compression ratio on a normally aspired engine, to benefit from W/M injection. However it does work well on boosted applications, IF IT IS TUNED PROPERLY. It is not plug and play.

Someone posted about nitrous, and CO2. That can be used to spray an intercooler, but do not let it get into the carb. CO2 will not burn and will cost HP. N2O will lean the mixture, and cause internal engine damage, if fuel is not added, also.