Testing for air leak on manifold

In my quest to find the source of a misfire it was suggested to test for an air leak on the air inlet manifold by spraying contact or brake cleaner over the joints. If there’s a leak you will hear the engine revs increase. If there were a way that air was getting into the vacuum side of air intake this would cause a weak mixture and subsequently a misfire. Tried it and it would appear I have no leaks.

I squirted a little into the air filter and the engine revs increased so it see.s a good easy way to test for air leaking into the vacuum side of the engine.