fuel pressure problem

[Hammered]

I also have to question your regulator being on the return side.

Isn't this the norm for return systems?

[Vegas69]

Depends on the regulator and application I suppose.

[MonzaRacer]

OK on fuel injection with a return you use the regulator on the return side as its a return regulator it lets a certain amount of fuel/pressure by there by regulating the pressure/volume.
As for this with too large a line you have a collum of fuel weighing X and then subject it to large amounts of G forces, take a gallon of gas and swing your arm in a circle and see how heavy it is underload.
Your Walbro is sufficient but you need a booster pump amidship, let tank pump push/pull fuel then let next pump keep engine fed.
Also make sure you have a good regulated powersupply.
Jacobs Electronics makes good units and they will keep large by huge amps fed with voltage.
fuel pumps need heavy relays, I use the oval GM relays as they can handle 70 amp surge by design but are like a 40 amp rated unit.
Put a Gmeter on your car, it may be emparting too many Gs to the mass of fuel in a 1/2 in line.
As for needing same size line on return, thats bs. Pretty much any of the setupsI have built the regualtor will bypass no more than 70 percent and it decreases as engine demands go up.
Another way to test this theory block off the return line ifit goes away you may be limiting the engine by having too low a regualtor setting or the TBI may need bigger injectors or the ecm need the software up graded.
But your readings on the fuel psi tell me to go for blocking the return and see what happens, if it goes away yon may need to use a restrictor pill in return to help regualtor keep up as it may let too much fuel back to tank.
Lee Abel
AFTERMARKET PERFORMANCE