[Ed Wright]

Makes more difference with an EFI car. Voltage level effects how fast the injectors open. I found when my 12 volt batteries were a little low, my logger showed it running leaner. That, of course, effects consistency. I had a button under the accelerator pedal, hooked to a relay, that shut the alternator off @ WOT.
Going to two 16 volt batteries cured all that. With no alternator. Had to lean it down with 16 volts batteries. The injectors opened faster, of course.