If you're certainly not using a factory-style EFI distributor, MSD and Holley use a vast range of reps that plug straight (or even via adapter harnesses) into aftermarket EFI devices. These not simply supply a RPM sign but additionally make it possible for the EFI system to control ignition time.

If you’re certainly not using a factory-style EFI distributor, MSD and Holley use a vast range of reps that plug straight (or even via adapter harnesses) into aftermarket EFI devices. These not simply supply a RPM sign but additionally make it possible for the EFI system to control ignition time.