With out hearing it it's hard to say. Are you comparing the noise with the intake tube off or on? I don't want you to think I'm calling you dumb or anything. In a situation like this I usually find it's something very basic that I did wrong. Are you sure the bolts are tight and that the manifold is flat? When you put it all back together you have to tighten the bolts where the 2 pieces meet first and then the bracket in the back. If it's not flat then it can create a vacuum leak that will cause noise but not affect running because the leak is even in all cylinders. Also it doesn't take much of a leak for you to hear it.... These are the kind of things I have run into.
