that is the air intake, it should have two of them, one with a tube connected to the intake manifold (in the engine), and that one... that one is called a resonator, or to make it easier, just buy whole the air intake..... or it would be better if you buy some other kind of air intake, anything but stock... stock sucks... buy a short ram air intake or cold air intake... their better than stock... more HP... and short ram intakes will cost the same or even less, depends on what brand you choose.... but CAI(Cold Air Intake) will cost a lot more..) but they're better
PS: r u a newb???