Fuel Pump / Fuel Rail Pressure Issues

After installing a larger (or secondary) fuel pump for my EFI engine, the fuel rail pressure went up and my regulator won’t adjust it back down, what’s wrong?
To understand this issue, think of a fuel pump as providing flow, not pressure. A bypass regulator restricts flow, increasing pressure before allowing fuel to return to the tank. If pressure doesn’t drop when adjusting the stud counter-clockwise, the regulator may be too small for the pump’s flow, causing false pressure. Check the return line for kinks or size issues. During normal driving, the regulator and return line must handle over 99% of the pump’s flow without excessive back pressure. If either is too small, pressure becomes “false-high,” making it seem unadjustable and causing a pressure drop that mimics a weak pump. A good sign is if the regulator can adjust 3-5 PSI below the desired base pressure, indicating it’s sized correctly.