if you want full manifold vac. then you need to set your dist. up for it. i'm running full manifold vac. in my car. initial timing is at 14* but at idle with the vac advance its at 30*. the car idles smoother, is peppier at lowwer/cruise speeds and light throttle and it seems to be running about 5* cooler.
i have 20* mechanical advance ( all in at about 3100 rpm) ad 16* of vac advance.
good thread about it here: look at greg_moreira posts...
http://board.moparts.org/ubbthreads/showflat.php?Cat=0&Number=6813633&an=0&page=0#Post6813633