Yes, like a water/meth injection system. I had one on my last car but it was Supercharged to 10 psi. The water/meth injection system added 28 hp and 25FPT.
ORIGINAL: choodock
However, injecting water into the engine should lower the intake charge, creating a more dense volume of air.
I am not an engineer, I am just blabbing stuff off the top of my head.