Initial timing

I was able to duck out to the shop for a few minutes. Started up and raised slightly above idle it stumbled, then I pulled vac hose from front of carb and stumble went away.
I have a spare 8.5R va, I'll swap out the 11R that's on it.
Dumb question...could something be causing too much vacuum OR vacuum too early?
Thanks
I mentioned in an earlier post to swap out the vac adv canister . I had the same troubles 273 commando .. new can solved the issue. ..