Whining noise at low speeds

Hi Everyone - I was wondering if I could get some diagnostic help on my 2008 Nissan Altima 3.5SE (V6 CVT Sedan).
I'm hearing a speed-dependent whining sound at low speeds (audible
when driver window is down and driving near a sound-reflecting surface like a wall or some parked cars.)
It starts up as soon as a start moving in DRIVE from a stop (pitch increases with speed). When I let off the gas, the sound stays present as I coast, reducing in pitch as the car slows down. Shifting the car into neutral while coasting does not affect the sound, nor does revving the engine in neutral while coasting.
The noise is not present when at a stop in neutral or park.
Any ideas what this may be? FYI I am running an aftermarket short-ram intake and a cat-back exhaust system. The dealer pointed at the intake as the source/cause of the noise, but I don't see how that could be consistent with my symptoms.
Thanks in advance for any opinions and advice...would really appreciate the help!
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