Is your air filter housing sealed properly? I occasionally forget to secure the inner clamps and it makes a noise between 2-4K RPMs that I'd describe as loud gurgling.
Is it just the normal resonance noise that you don't notice because the car doesn't spend much time under load at lower RPMs? Occasionally the car won't downshift when I think it should (auto) and attempts to climb a hill in too high of a gear. It seems like if the load is high and the RPMs are low (under 2k) there's more intake noise (which sounds impressive, but nothing much is happening in the acceleration department), although maybe the VQ30 lugs like no engine I've ever heard. More throttle (often almost to the floor) and a downshift later the problem disappears.