[~The Jester~]

No, the exact opposite happens. Provided an ample and adequate supply, as pressue INCREASES, volume DECREASES. Picture holding your thumb over the end of a garden hose. Pressure?? Hell yeah! Volume?? Not so much.

If you're tuned correctly, fuel pressure shouldn't affect rich/lean one way or the other. Let me state that I'm referring to a CARB here, not sure what you're running. Anyways, the carb will take what it wants/needs/is available. Except for extremes Rich/Lean is your TUNE, not fuel pressure. Extremes being fuel starvation will cause a lean condition, as blowing past the needle/seat (or float levels set too high) will cause a rich condition.