To test for intake leaks, I occasionall spray starting fluid at all suspect areas (intake boots, crank seal, etc) and wait for any change in the RPMs. Hasn't ever worked for me, but it also hasn't lit anything on fire either.
Also, careful what your spraying brake cleaner on since it eats some seals, gaskets, plastic and rubber. Although I'm not sure it's a good idea, I like to loosen up dirt and grease with electrical contact cleaner. Seams to work as well as brake fluid and it's safe on most plastics and rubber.