Your car currently will have a 4 catted h-pipe. That's a piece that exits the headers and crosses each other as an H before meeting the mufflers. An X-pipe is the same but meets as an X-crossover before hitting the mufflers. You can get a catted pipe or an off road pipe. The off road pipe is built for racing, etc, but many people use them on the highway because of their performance and because the missing cats make the car much louder than stock. In order to use an off road pipe, you usually need a MIL Eliminator, which is an 02 Sensor simulator for the back 2 sensors. They will keep the check engine light from tripping. Cats (catalytic converters) are emission devices to reduce exhaust scents and carbon dioxide. They have a ceramic material inside them. If you want a louder car, go with an off road pipe with performance mufflers (Borla, Magnaflow, Flowmaster,etc) and you will have a car that sounds how it runs. You can get a high flow catted pipe and stay legal, and still make the car sound good. Before you go with an off road pipe, make sure you can get by the law. You can usually purchase a whole catback system and mid-pipe for 400-800 bucks. Hope this helps, and I hope I didn't go too far...
