There are two types, I believe the one you are referring to is the resonator bottle that is located on the intake pipe right before the throttle body. If you take it off, you will hear that your car sounds a little bit better, but it is heavily disputer whether or not it actually gives you performance gains. I think that there is a quicker response when I press the pedal, but many people say that it is a waist. To remove it, you similpy undo the clamp that holds it on, and put a medicine bottle top back in and clamp the top in tight. That is it.
On your exhaust there is a thing called a resonator and it serves the same purpose as the resonator bottle in that it is designed to eliminate pulses in the air for a smoother, more quiet tone. As a result both are somewhat restrictive. If you were to remove the resonator in the exhaust, I would think that you would see some performance gains, but again not huge ones since you dp and all the cats and mufflers are very restrictive.