vacuum gauge to solve idle issue

If you want to watch full manifold vacuum at idle it would be the port on the right front of the carb.
It's easy to tell which is which by putting your finger on the port at idle as the right side port sucks all the time and the left side only sucks when the throttle is opened.

If it were my car I would pull the idle mixture screws and blow some air in them and see how it does after that.
Surging is usually a side effect of a lean condition, so the idle circuit might have some crap in it.
Just count how many turns the needles takes to bottom out, so you can put them back where they were when you put them back in.