While performance gains vary depending on the vehicle you can expect a gain of 5% to 10% in horsepower and torque. For example, with a 2005 Chevrolet Silverado with a Duramax diesel engine you will see a gain of 18 HP. and 28 ft/lbs measured at the rear wheels. You can also expect a reduction in exhaust gas temperature (EGT) by approx 200º F.