Fuel Injection Pressure Regulator. EST, MON to FRI. Adjustable Billet By-Pass Fuel Regulator. Has been the undisputed leader in fuel systems for over 100 years. Holley carburetors have powered every NASCAR? 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 […]