Holley Sniper. From their instructions:
"We recommend at least a 3/8” feed line and 3/8” return line."
"The Sniper EFI system requires a return fuel line to the fuel tank."
"The return line must not present a pressure restriction to the return fuel flow. There should never be more than approximately 3 PSI of pressure in the return line. A line that is too small, or has restrictions will cause tuning problems with the system."

Now, I watched one of their videos that says their in tank pump has a built in return, so an external regulator and return is not required. Waiting on a response from them to clarify is this pump, with the Sniper, still requires a return line or not.

https://youtu.be/n8Avatc3fd4