It's not just the regulator, but also the entire return side of the fuel system. I've found that I can get away with using a high volume/pressure pump as long as I have at least a 5/16" return line with no restrictions. If it's a 1/4" return line (like on an early Mustang tank with an EFI sending unit), then the restriction is too much for a low pressure TBI fuel system, yet is fine with a higher pressure multiport system.
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