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08] Manipulating horsepower is as easy adjusting fuel pressure. With the fuel pressure at 7 psi, our tune was rich, with an average of 11.8:1. We left the rest of the tune the same and dropped our fuel pressure to 6 psi. By dropping pressure 1 psi, our A/F reading went to an average of 12.8:1, and also showed a loss in power throughout the pull. We put the fuel pressure back to 7 psi and changed the air bleeds them from number 30’s to number 33’s. With the air bleed change, our average A/F reading was now 13.2:1, which is where most people will tell you to run. In our case, our power was down even further than before.