A simple, effective vacuum leak checker that leaves no mess at all is a Propane torch. Just crack the valve open a little and search for the leak. The engine will rev up or smooth out when the gas gets sucked into the leak and there's no liquid to make a mess like WD 40 or carburetor cleaner leaves behind. I've also used acetylene from the torch to do the same test.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!