Well, the second new FP and FF came in and and are installed. Still the fuel pressure low, 5.1 bar.

So far;
The tank has been flushed twice with clean fuel,
Two new Bosch Fuel Pumps,
Two new Bosch Fuel Filters,
New Bosch Fuel Accumulator,
New Inlet Fuel Filter,
Rebuild Fuel Distributor. Build went back together without using the case screws for anything but guides. The only pressure used was light finger pressure to slowly squeeze the two halves together,
New EHA Controller,
New Pressure Control Valve.
From there it returns to the Fuel Tank.

There are three gallons of fresh fuel in the tank. I have the FD just setting over the Plenum with no fuel pipes hooked up. The car is setting level. Start the fuel pump against "0" pressure. Watch pressure steady build to 5.1 bar and hold. I purge the fuel test gauge and hose system to vent any air, and still no change. The system holds 3.0 bar, dropping to 2.0 bar in one hour. There re no visible leaks of fuel

I have had the first fuel pump produce 6.4 bar for a brief time. The second has only produced 5.1.

The only possible thing I can think of that I can think of is the Fuel Tank Cap?

I tried to adjust the DP at the EHA. Turning the adjusting screw in 1/4 turn and testing again went like this
1 QT in, no change
1 QT in, no change
1 QT in, slight resistance felt at the end of the adjustment, no change
1/2 T in, same resistance, no change.
At that point I stopped.

Any ideas would be welcome.