Call me crazy but here is how I found several vacuum leaks on my car:

It involved using my shop vac in blow mode and stuffing the hose into the car's air intake. I had to open the throttle manually of course to let air into the manifold. Also, I had to devise a way to let most of the air pressure escape so as not to blow all the vacuum hoses off. I figure there was maybe a couple of psi in the system, not too much to damage anything, I reckon. I then applied soapy water to all the connections and manifold joints.

This also worked for finding exhaust leaks.

Was I wrong?