I thought the pcm set the pressure at what is needed. Please explane it for me. Thanks Alan

 

It only helps on the '93 model. In other years the PCM will adjust the fuel injectors to compensate for any fuel pressure changes. To be accurate the PCM doesn't monitor fuel pressure but will notice an increase in richness through the O2 sensors and will adjust the fuel injector accordingly. You will feel a good gain of about 10HP at first but after the PCM takes its readings that gain will disappear. This isn't the case with '93 models as they don't contain this ability.