I mention this with a note of caution because it can make you a candidate for the Darwin Awards.

With the engine at idle, spray some either or brake parts cleaner at the hoses and connections and listen for the idle speed to go up.

The ether gets sucked into the vacuum leak and changes your fuel air mixture momentarily, and lets you know about where the leak is.

This would probably not work with a F/I engine since Lamda Sond is supposed to smooth that stuff out, and the ether might fry the O2 sensor.

I learned that trick from an old mechanic with no eyebrows.
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'70 145, Webber converson, trying to keep it stock other than that.