Well the air silencer does just that. You can expect to hear a bit more of a whoooshing sound when you accelerate without it.
It is just simply there to make the operation of the vehicle more quiet. Honestly, I didn't notice much difference when I pulled mine.
As far as benefits, you may gain a bit more power, a tad more MPG. Nothing to write home about, but a very simple way to gain a little bit...and free....
cheers,
Andy