Answer is: Increased pressure would increase the rate of forming water vapor.
According to Le Chatelier's Principle, the position of equilibrium moves to counteract the change, the position of equilibrium will move so that the concentration of products (water waper) of chemical reaction increase, if:
1) decrease temperature, because this is exothermic reaction (ΔH is negative).
2) increase concentration of reactants (oxygen and hydrogen).
3) increase pressure of the system, so reaction moves to direction where is less molecules.