A bypass regulator for EFI systems, carrying three AN10 ports. AN10 is the significant figure here: this is not a small-engine regulator but one intended for systems moving substantial volume, where an AN6 unit would itself become the restriction. Injected engines run far higher pressure than carburetted ones, and a bypass design returns surplus fuel to the tank continuously so rail pressure stays flat rather than surging as injector duty rises and falls. That stability keeps your fuelling calibration honest. Pair it with a boost reference line if the engine is forced induction, so rail pressure tracks manifold pressure and injector flow stays predictable.