Every car, truck, SUV, or motorcycle requires some type of exhaust system. Low backpressure and high exhaust flow rates are achieved by directing free-flowing exhaust gases through smaller perforated steel tubing. If you do it yourself, you may find that you can build your own high-performance BMW exhaust system with relative ease.
If you want the best exhaust system, you need to monitor backpressure. The myth says that you need more back pressure to get the right amount of torque. The reality is that if you want the highest exhaust flow, you want lower backpressure. They require a column of fast-moving, free-flowing gas to create a vacuum wave behind the valve as it opens. This allows the exhaust cylinder to move faster without large pump losses.
The exhaust system is only as good as the exhaust on the other end. This can kill your exhaust system if not designed properly. Yes, the standard exhaust is designed to be quiet. However, these devices are often designed with a maze flow that slows and cools the exhaust gases. This can be good for your exhaust vibration; However, it is not good for your fuel flow.
Any kind of restriction weakens the power-generating mix trying to reach your engine. Your engine will also not perform properly with a diluted intake fuel mixture. There is a loss of power from the engine and this actually makes it harder to pump the engine to empty the cylinders. Instead, you need to make your own rectangular exhaust.