[rotrex]

Water, if it makes it into the cylinder as a mist, will slow down flame development and flame front speed. Effectively, the mix burns slower. If you do not add ignition timing to compensate, you'll lose power over no water. Adding methanol reduces this effect to a degree as its flame front speed is faster than gasoline. Still, as a 50:50 mix by weight, you need to add timing.

Now if you are lucky, you might gain a tiny wheeny bit of power by cooling the intake air. But don't overestimate this. The main effects are happening in the cylinder and effectively increase knock resistance while reducing flame speed.

The more you inject, the bigger the effect. Without tuning, your AFR will drop making things even worse. You will significantly lose power without tuning for it.

Once you tune for it, especially with direct port injection, it works really well.

If your engine can be tuned for max torque without being knock limited on water meth, you have to increase boost for further gains. Once you become knock limited regarding power, just inject more mix. You can do this until to insane power levels given your engine and GB takes the beating.