A QUICK QUESTION ABOUT MANIFOLD VACUUM

I was wondering if the vac source location plays a role in it?
No dial back timing light. I can lean out the mixture with the a/f screws to get into the 13's.

I just found it strange that the mv is perfectly stable at idle, and gets a little erratic in the fast idle zone. I might try the vac gauge on the manifold fitting instead of the car base and see if that makes a difference.

I was just concerned that it may be a vacuum leak........I tried a propane torch around the carb base and intake with no change in rpm.