You may need to get a hold of a modis scanner or an actual ford scanner. Some of the general scanners wont show some codes. I think the 7.3 fuel system is similar to the 6.0's so i would check the IPR (injector pressure regulator) sometimes the screens get dirty. Heres a
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Or it could be the ICP sensor (injector control pressure)
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Try to get a hold of a scanner before you start throwing parts at it.