Question for all those on manifold vacuum

[jcd9730]

I've tried to run the advance off manifold vacuum, and it idles like crap.

From what I understand, the vacuum can is set to start advancing at a certain level of vacuum by a limiter, ie at 10Hg and then advances until full deployed.

My question is, if I have it hooked up to manifold vacuum, that means at idle the vacuum can will be seeing full vacuum (17 -18Hg in my case) right at idle. This would then fully advance the timing, right at idle and cause it to idle like crap since there is way too much timing advance at idle.

Right?

I just don't see how it would work with manifold. I'm not disputing that manifold is better, I just don't see how this works