A performance exhaust header takes the place of your car’s original equipment exhaust manifold. A regular exhaust manifold is very restrictive to exhaust flow. Restricted exhaust flow limits the amount of horsepower that your car’s engine is able to produce. Performance headers are designed to maximize the amount of exhaust flow from the cylinders into the exhaust system. This is done by reducing what is known as backpressure in the exhaust system. Backpressure is the resistance to the free flow of exhaust gases through the exhaust system. When you limit the backpressure by installing headers, you make the engine more efficient, meaning more power and better mileage.