I was under the assumption you tested fuel pressure at the Schrader valve which is on the passenger side fuel rail. If this is incorrect let me know cause I am trying to verify correct fuel pressure on my L.

Thanks,
Mark

 

My Pal Terry R. has some info here that may help

http://www.southfloridapulleyhq.com/...ng/fs_afpr.htm

This Adjustable Fuel Pressure Regulator and Gauge Kit is needed to adjust extra fuel pressure when using the Upper & Lower Pulleys, that generate between 13 to 15 pounds of boost pressure, along with the reprogramming of either our Performance Chip or the Performance Flip Chips we offer. You can safely adjust the fuel pressure, upwards from 40 lbs. static to 42 lbs. to help eliminate knock retard that will be present with the modification packages we recommend!
APPLICATIONS: 1999-current Ford Lightning
PRICE: Adjustable Fuel Pressure Regulator & Gauge Kit $195.00 shipped

 

If the L has return style fuel system, then you need to test before the regulator for an accurate high pressure reading. I don't have an L but this is universal info anyway. Fuel after the regulator just goes back to the tank and is low pressure. Your schrader test port on the passengers side is a high pressure source, so this will give you an accurate reading.