Designed for use with our Pro/Elite/Ultra Elite Boost best drive pumps, or similar style pumps in a carbureted application. -8AN inlet and outlet ports with a -6AN gauge port. Boost reference port is tapped 1/8 NPT and can be used with push lock or AN style fittings. Regulator model #706021 is designed for use with our Pro Boost pump. Model #706023 is designed for use with the Elite & Ultra Elite series pumps and utilizes dual return lines allowing lower idle fuel pressure and boost reference capable over 1:1 at wide open.