You have a computer controlled engine. Adjusting your fuel pressure is a waste of time other than it will probably idle a little leaner. Since your MAF is calibrated for 24# injectors your computer knows how long to open the injectors to supply the correct amount of fuel.
Our computers adapt to changes in fuel pressure. If you noticed an improvement at the dyno, it's likely that your O2 sensors are old and need replacing, or it's possible that your engine runs better a little leaner. Any changes that were made have been adapted to by now, however, and are most likely gone. See the Fuel Pressure thread for more details.
A fuel pressure change will only change your air/fuel curve temporarily until the computer adapts. The only way to adjust your air/fuel curve permanently is with a chip or a computer like the SpeedBrain.
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351W 89 Mustang GT Convertible