We run a Walbro 392 pump on our turbocharged slant six, with Holley double-pumper 600 4-bbl and have ZERO problems using an Aeromotive regulator that adjusts the pressure down to 6psi with no boost, which the carburetor likes. The regulator has a 3/8" supply with a half-inch return, and that setup provides a steady 6-psi gauge reading, for the gas coming out of the regulator under all circumstances.
The secret to running a high-pressure pump is the regulator and the return line. We didn't get satisfactory results until we increased the return line from 3/8 to 1/2"... Don't ask me why; I can't answer that... I just know it worked.