I use an unlit propane torch around vacuum connections at idle. Follow the vac hoses for cracks or splits that are tough to see. Run it around the air intakes. (Throttle body and intake manifold)
If there's a leak, the idle will smooth out or raise up. Don't forget about the CAD vac lines.
People use carb cleaner the same way. I don't because it's flammable. If you use carb cleaner, have a fire extinguisher handy. carb cleaner works well and it's normally safe.
What happens in my Jeep, stays in my Jeep