What's with the "East Wing Annex" on the stock airbox?

[TURNz]

You know, the extra hallway of plastic that juts toward the driver side on the air intake?

 

[gat0r]

resonator, to quiet the engine sound down

 

[iamdub]

^Yup. Resonator, muffler, whatever. It attenuates the sound waves produced by the engine sucking pulses of air through a plastic tube. They do (I think there's others besides that one you mentioned) disrupt the air flow a little (small loss of power), but this is a sacrifice made by GM engineers in favor of a quieter engine. I replaced my intake tube with an MIT and it sounded like I had a performance muffler. The growl sounds great and is only heard when getting on the throttle. You won't hear it when cruising.