I believe in vaporization the strength of the Hydrogen bonds stablizes the molecular equation and maintains the two hydrogen to one oxygen atom ratio. And if for some reason the one oxygen atom was released there would be two hydrogen atoms now available for combustion, hydrogen being highly combustible and having high thermal conductive properties (and a mute point since it don't happen like that). In reality, the water vapor ends up going out your tailpipe and becoming condensate along the way as it does. IMO the engine stumbles on too much water due to other reasons (like drowning in water and not enough oxygen). The biggest risk I know of to lean in meth injection is if someone tuned an enrichment table for meth and then their meth failed.