I have a 2006 4.8 ls engine and it only has one line at the fuel rails, the feed line. There is no return line nor is there a regulator. See below.
So I understand the factory fuel pump has the regulator, filter and pump all in one unit. Below is an airtex E3609M. Which is like an OEM replacement.
So if the OEM pump has the regulator, filter and pump all together, why are there return lines in the top?