Where do vacuum readings need to be taken from? the test port on the mixer?

I put the spark testors on it, nice crisp blue spark throughout all speeds, even when the engine is coughing and sputtering.
the only thing I haven't changed is the diaphragm and spring in the mixer. I have seen other diaphragms but never another spring? I did put the red spring in the regulator.
This thing has me confused.