[CGGorman]

Pumping doesn't do anything in a fuel injected car, but holding the pedal to the floor ~usually~ stops the injectors to help clear a flood situation.

Sounds like you have a (or multiple) leaking injectors. I'm not sure how long it takes for a properly functioning fuel manifold to bleed off pressure, but it may be helpful to check you fuel pressure at the manifold after shutdown and see how long it takes to bleed off...