Distributor Vacuum Advance?

AbodyJoe,
Few errors/misconceptions in your post.
- once the PVA port is exposed, the actions of MVA or MVA are the same. Both are exposed to manifold vacuum. There is no difference.
- your claim of detonation at WOT with the example of 34* + 16* VA=50* is incorrect, because the VA [ MVA or PVA ] drops to zero at WOT. Timing at WOT would be 34, not 50*.
- minimum vac of aftermarket VA cans. Crane & others go down to 6~7" of vacuum.