Like other exhaust systems, the Cat-Back version carries burnt gases away from the engine to open air. Because they are generally larger and flow better than stock systems, they are able to move exhaust gases out more expeditiously. Keeping your Jeep Wrangler JK's engine clear helps improve fuel efficiency and performance. Installing cat-back systems may also increase horsepower and torque. Since they emit more gas than regular exhaust systems, they tend to make a bit more noise. Of course, this isn't a problem if you intend to take your JK off-road or enjoy the sound of your Wrangler JK. The smooth, deep tone of the cat-back exhaust system is as impressive as it is itimidating for lesser Jeep Wranglers. Throw on a new header setup or Mid Pipe and free up even more of the power being lost through the restrictive stock exhaust.