The computer probably took a little time to adjust to the change. Before it had to open the injectors more to compensate for the lower fuel pressure at the fuel rail. Now that there is a higher pressure at the fuel rail, the computer can back off the injector pulse width (amount of time and magnitude that the injector is open). Changes like that can sometimes take some time to come back to equilibrium.
Also, could it be possible that the new found throttle response cause you to drive extra spirited for a little while until you realized how much gas you were burning? Just a thought.