Manifold Vacuum Advance what am I not getting?

FWIW, I have my hei problems sorted now, set the initial to 10 btdc with no vac adv. I connected it to manifold vac this morning. Restarting was immediate and improved, dropped the idle back down to where it was without mva, no stall putting it in gear. Combo is low compression, mild cam 318. The adv can I have installed on the reman distributor is dual port and not adjustable. If it is too much on the test drive, I will just swap to an adjustable advance to tune it. Good enough for me.
Manifold vacuum can work for some combos, but I always say be prepared to swap it back to ported, because it doesn't work for everything. Very simple to swap back and forth.