Tracking down vacuum leaks sucks.
Easiest way I've found is use a propane bottle torch. Old school knob valve. No fancy piezo igniter stuff. Don't light it. Just open the valve and put the nozzle on every connection there is. Ones that leak will suck some propane in the intake and the engine will speed up.
Engine idling obvs. Also outdoors only.
that is smart..... i have a scooter i've been trying to sell that got a vacuum leak someplace. I found a general area previously by spraying carb cleaner around, but thats really hard to track down and just damn messy. A propane torch with super low flow rate should be able to identify the area with a lot more precision.