4 Port VR Series Fuel Pressure Regulator Four Port Adjustable 4 to 9 PSI Boost Reference 11 HolleyThe Holley Vr Series billet fuel pressure regulators are part of the VR1 and VR2 Series brushless fuel systems product line. These regulators can support 3000+ horsepower engines that require high volumes of fuel flow. Both EFI and carbureted versions can be referenced on a 1: 1 ratio. They are precision machined from 6061 T6 billet aluminum for strength and durability and feature a black bright dip anodized body and a clear bright dip anodized top