AFE Exhaust Systems are designed to replace the original equipment unit on your Diesel Truck. The AFE Large Bore 4 inch HD Diesel Exhaust System adds up to 5 horsepower, increases torque and flow, improves your fuel economy, no welding required, 4" mandrel bent tubing, smooth bends, and adjustable hangers. Choose from aluminized steel in turbo back, cat back or tom kit. aFe air intake systems and filters are very good at getting air to your engine faster and more efficiently. However, aFe realized that it is important to get the air out as well. Just like anything else, the more you ingest, the more you need to expel, otherwise things can get clogged up. That is the reason why we offer exhaust systems to go along with our air intake systems. It is a natural extension of our efforts to enhance the science of airflow management in performance vehicles. This is especially true in the diesel motor which is simply a huge air pump. Since diesel engines are a compression ignition engine and modern diesel-powered vehicles are turbocharged, the more air you pump in, the more power you generate. However, which turbocharged diesel, it is very important to get the hot exhaust out or the Exhaust Gas Temperature (EGT) rise to critical level that could damage the turbo itself. Most OE manufacturers offer a restrictive 3 1/2" exhaust system which is fine for normal every day city or highway driving. But you bought a diesel truck for its towing or work capabilities, didn't you? If so, you want more power to go up that grade towing your boat, trailer or tools. Getting the air in will give you more power. Getting the air out will give you more power. When you get more air in and out at the same time, you get a lot more power. With the 4" exhaust systems are mandrel bent aluminized steel which eliminates the sharp bends and kinks that the factory stock exhaust systems have. The aluminized steel resists corrosion as well as stainless steel but is priced more economically. Our large 8" diameter straight flow through mufflers do a good job of letting the air out as well. You do have the option of turning the muffler around for better flow or quieter ride. The 5" diameter Exhaust tips finishes up the entire system for a nice throaty sound and appearance enhancement. aFe entire systems comes with adjustable clamps, muffler and sectional tubing for easy installation whether you have a standard, extended or crew cab vehicle. (Exhaust tips sold separately). The kits includes Turbo-Back, Cat-Back or Tom-Kit with Muffler Delete Pipe (as specified), All Hardware & brackets needed for OEM installation and installation instructions.