[Nisbo]

Definitely sounds like you guys are referring to the intake whistle. It is definitely more apparent if you have an aftermarket intake installed.

The location of the whistle seems to be the passenger right side footwell, slightly below the dash. I think there is a rubber grommet where all the electrical comes into the passenger compartment in that general location so the whistle from the intake which is in the passenger side front fender comes into the passenger compartment.

Here is a test you can try. Remove your intake filter and drive it around the block. That whistling you are referring to should increase tenfold. If it wasn't the intake, keep searching.