Yeah, the car felt more responsive without it, it's for quieting the intake since the resonator is right by the airbox, the intake can't be too for it to work at all. It's not too cool right on top of the radiator either, I'm sure the air is cooler by the airbox, not to mention the rectangular inlet and funky bends that restrict it.

Also if you get any header, you'll notice a significant difference, the stock Si manifold is fucking terrible, not to mention heavy.