Bah humbug. I noticed the hissing this evening in almost the exact same spot. I used the Carb Cleaner/Ether trick to approximate where it is and it's right by the EGR. Tightening the EGR did not help.

Guess I'll try the tube trick and order new gaskets tomorrow

Good thread - here are some keywords to help the search engine.

intake gasket leak hissing rough idle surging stall stalling vacuum gas mileage howl whistle