Ok just a trick I learned to find a leaky intake...
Not the safest way.. With the engine running (idle) spray starter fluid near all the seam line around gaskets, hose fittings etc. just a little bit, what your looking for is a sudden increase in speed.
Go slowely around any suspected gaskets or vacuum lines . If the RPM'* surge go back untill you find the spot. Worked for me more than once on leaking gaskets and lines..
Be careful with the starter fluid and the nuckles in the fan and belts.. One of those spray tubes helps.
Good Luck BB