Fuel Pressure drops under Full Throttle Boost..Help Needed

Hello team,
I have this strange situation, where my car is moded with the following:
- Ford Aluminator 9.5 (low compression engine for boosted applications)
- Procharger D1SC
- Lethal Performance Dual Pump Fuel System (return style)

Recently, noticed that under Boost, 1st, 2nd, 3rd Gears wit WOT, fuel pressure is perfect, then in 4th gear, fuel pressure drops from 60psi to 15psi (making car goes very LEAN)..!!

So, I investigated the Fuel Pumps, and found one of them leaks a little bit, so I changed it, ended up with 2x WALBRO Pumps (1x 400lph, and 1x 450lph).

Now, made the test again, with the same result, perfect FUEL PRESSURE in 1/2/3 gears, and in 4th drops again and goes lean.

Any advices? what to check?
- Is it something might caused by ( weak battery - Voltage )? if yes, how can Identify this?
- Is it something related to the Fuel Controller (that piece in the trunk behind the back lights) might be faulty and not able to send the correct signal to the pump?

Ultimately you’ll need to datalog and have your tuner check it. When I first bought a return style fuel system, it was a budget system that used the Stock fuel rails. 2011-2014 stock fuel rails are NOT return style. I was rich at idle, but lean up top. Switched to a true return style fuel rail and it solved the problem. Ensure you’re straight from the pump to the rail, then to the regulator.

Check the fuel filter and the check the diaphragm in the FPR. Are u sure the 2nd pump is coming on? Sounds like the second pump isn't activating.

since its not lean in 1st 2nd or 3rd that means your fuel issue is either heat, time or capacity related probably a bit of all

as a test try making a wot pull with the fuel tank completely full