Holley Fuel Pressure Regulator Diaphragm 12-818 | Holley products have been the undisputed leader in fuel systems for over 100 years. Holley carburetors power every NASCAR Sprint Cup team and every NHRA Pro–Stock champion. Holley's products include performance fuel pumps, fuel injection, intake manifolds, cylinder heads & engine dress–up products for street performance, race and marine applications. As a single solution, or partnered with products from other Holley companies, Hooker Headers, Flowtech Headers, NOS, Weiand, or Earl's, Holley products can give you the edge you need over the competition.