When talking about intakes, what exactly will make an intake hiss? On my 3.5 between 3,000 and 5,000 RPM I get a very loud, distinct hissing sound. It sounds similar to a turbo spooling up. Now, does this typically mean that the intake is restrictive, or is it something else? It made this sound with everything stock, and it'* louder even with my gutted airbox setup. It'* not a bad sound, I'm just looking for the cause of it. I'm not going to drive around without the air intake on either to test it.

Hoov, your 3.5 make a hissing sound under heavier (not WOT) between 3-5K rpm?