I guess the way I see it is if you have an engine that starts fine with the static advance setting and it idles good, then ported vacuum is the way to go. If you have an engine that idles good with more advance than allows for starting with out kickback, then manifold vacuum is the better one since you can retard the timing to allow it to start and then have it advance a set # of degrees with the vacuum to where it idles good. So at WOT, both manifold and ported vacuum signal will drop significantly and mechanical advance takes over at that point correct? Sorry for all the questions, just trying to educate myself on this subject