You are probably referring to the Intake Resonators...or whatever you want to refer them as. All intakes eliminate these. You can probably find a suitable plug to delete it if you want. Just make sure it seals properly.
Are you referring to the little part on the underside of the Intake Tube. It is partially visible in the FAST parts breakdown. The reason you cannot find it most likely is due to the fact that Nissan does not list them separately.