taking the muffler off will just make it loud as shit and very annoying. You can buy things called "Test Pipes" that are basically a pipe that takes the place of the CAT and allow you to still use your o2 sensor. It might make a slight change. You are better off on just buying an axle-back exhaust if you just want sound changes. Look at Apexi for exhaust, they make good looking (no fart can) And very well built products.
This all depends on what your local laws are about exhaust or emissions and etc.
