Out of the box, mine had 28° of mechanical advance that came in by about 3000, and terrible spark scatter. The newer ones have an adjustable plate under the reluctor. There are 2 T-15 Torx screws that you loosen to slide the tabs in the slots open or closed to add or decrease total mechanical advance. I closed mine about 1/2 way and now have 14° of travel. It also causes it to come in earlier. I run 21° initial with 35° by 2800 on my 496" stroker. The spark scatter was hepled greatly by siding a length of 1/2" rubber fuel line over the shaft, cut a long enough that it compresses about 1/8" against the oil pump drive gear when the distributor is tightened down. It acts as a dampener.

I do not run the vacuum advance.