[Tom Goldman]

The large MSD capacitor serves several functions ,as Rich stated it can help to minimize minor voltage fluctuations.
Its biggest function is noise suppression . The 7AL can cause a lot of RF interference ,which on a car with absolutly no other electronics probably wont cause any problems .
Problems begin when adding other electronics such as an RPM shifter control , a Data Recorder or a delay box , all of which can be subject to RF interference.