Carpet, dash (create your own dash with essentials only), passenger seat, spoiler (if you have one), replace power sh*t with manual sh*t (if they make roll-ups and the like for 2gs), center console, ligher wheels, carbon fiber hood (or complete front clip), etc.

The sound deadener is usually painted over. It's adhered to the metal of the interior of the car. It is apparent in that it has a rough texture, as opposed to sheet metal's smooth texture.