Several ideas.... One: the gasket where the 2 halves of the intake manifold has a split or small hole. Take some WD40 and spray at the joint where the 2 seal. Spray at the joint on the front and back if you can get too it. Spray close and heavy. If you get the right spot then the noise will change or go away... Two : you may have a vacum leak from a hose in that area. With out hearing the noise that's where I would start.... Let me know if that helps.
