FAST EFI HEI ignition modules will upgrade your current 4-pin HEI distributor to be compatible with today's aftermarket EFI systems. These simple plug-and-play distributor modules provide an EFI-friendly tach output signal—something that's not offered in OEM versions. And, it is that signal that allows you to easily upgrade without adding a tach module and the extra wiring involved. FAST EFI HEI ignition modules will provide improved performance over OE options, due to the addition of multiple-spark capability, which allows for a more complete burn of the fuel mix in the chamber.