1998 Ford Windstar Excessive Fuel Pressure

Got a stumper for ya fellas = My son has a 98 Ford Windstar =The problem started when the van died on him several times, ran poorly, and then finally would not restart. In fact it would not even turn over and crank. Since I live 4 hrs away I coached him and his brother inlaw with the diagnostics. I said that vans symptoms sounded like it was hydrolocked. They pulled the spark plugs and sure enough #1 cylinder was full of gas. They replaced all of the fuel injectors and it ran shortly and then stalled again. This time it flooded darn near all of the cylinders. I finally drove to Mn to see what was going on & checked the fuel pressure & discovered 90 PSI of pressure. Checked the fuel regulator and fuel spewed from the Vacuum port = AHA = Changed the regulator and still got 90 PSI = Disconnected the return line from the fuel line at the tank connection on the frame rail before the tank = No flow with high pressure - Disconnected the return line at the fuel rail & attached a hose to the rail = Pressure was now @ 27 PSI with good flow = AHA - Replaced the braided hose from the fuel rail to the stainless steel tubing behind the engine = "Still" has 90 PSI = Rechecked flow at the tank = Good flow now and 27 PSI of pressure = Removed the fuel tank - checked the plastic tube to the pump module = OK - Replaced fuel Pump = "Still" has 90 PSI = Rechecked return line before the tank = 27 PSI with good flow = Rehooked tube to the tank & pump = 90 PSI = Just in case I replaced the fuel regulator with one from another parts store ( Getting really frustrated now & grasping at straws ) = Same problem = = Removed tank & Pump again - Partially disassembled the new pump & inspected the return portion for possible obstructions that may have washed down the return line and possibly obstructed the pump = no debris = = OK guys - I am totally stumped = I am an ASE certified mechanic and have been wrenching for over 40 years = = What am I missing?