Best way I know of to find leaks is to hook your compressor hose up to the
throttle body inlet (I used the type of rubber stopper that goes into
carboys),  pump it up  with 5-15 PSI, leave the compressor running to
maintain pressure, and squirt soapy water everywhere there could possibly be
a leak. Engine off, of course. Works well on the exhaust too, only there you
stick the stopper in the tailpipe.

One surprising place I found leaks was the base of the "black column"
breather tube, whatever it's called. Easy to fix. The butterfly valve shaft
in the throttle body will also leak. Hard fix. JB Weld?

Anyway, it's much easier to see the bubbles come out than try to guess where
the air is going in.