Holley Fuel Pressure Regulator 12-843 HP Billet Fuel Pressure Regulator Fuel Pre. EST, MON to FRI. HP Billet Fuel Pressure Regulator. Holley® Billet Fuel Pressure Regulators are part of a complete line of fuel system products from Holley®. They are precision machined from 6061-T6 billet aluminum for strength and durability. They feature a black bright dip anodized body and a clear bright dip anodized top for corrosion resistance and good looks. The Holley 12-843 fuel pressure regulator features (1)-10 AN O-ring inlet; (2)-8 AN O-ring outlets. Holley® has been the undisputed leader in fuel systems for over 100 years. Holley carburetors have powered every NASCAR® Sprint® Cup team and nearly every NHRA® Pro-Stock champion for four decades. Now, Holley EFI is dominating the performance world as well as our products for GM’s LS engine. Holley’s products also include performance fuel pumps, intake manifolds & 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® Exhaust, NOS® Nitrous, Weiand®, Earl’s Performance Plumbing®, or Diablosport® – Holley products can give you the edge you need over the competition.