I know shimming is supossed to in crease your fuel pressure.what does incresing the fuel pressure do for performance issues and how does it affect you fuel milage.
Well, in general more fuel pressure is not exactly a good thing. More important is constant fuel pressure. I know nearly nothing about a 99 PSD and what it requires, but when you add more fuel with electronic mods and/or injectors you can pull your fuel pressure down too far during hard fueling. A bigger pump or modding something would help the most by keeping the pressure constant under heavy fueling runs. There may be a trick with the Fords that has to do with FP, but I don't know myself.
The teory is that the injector fills faster. Beyond that I am not sure what else it accomplishes. It definately does improve throttle response, and the truck is quicker though. I have it on mine.
