Initially, there was an engine, and it did require fuel and air in its cylinders to burn when a spark was introduced. However, there is always something left in the cylinder that needs to be removed by the exhaust system. The faster the exhaust can be exhausted from the engine, the faster the combustion process could start over - which giveth more horsepower. And so, we must taketh away the exhaust as quickly as possible.
This could come to pass if the twists and turns and mufflers that run along the bottom of the car could be eliminated. But again, alas, they cannot. They are required by those on high to keep our streets noise free and our air breathable.
But what if we promise to only bypass the exhaust system while we race safely on the track? Why, then we can install a Y-shaped vent. It should be inserted into the exhaust system between the engine and the muffler, "tilted" (since the short tube should be known), facing down and towards the rear of the car. When additional horsepower has been demonstrated to be required, a flange or block plate in the cutout can be moved into place manually or electronically to allow the exhaust gases to escape the labyrinth of exhaust system with haste. On the streets of towns, the cutout can be cut, allowing exhaust to travel through the entire range of systems such as catalysts and silencers.
Yea, verily, clearing quickly doth impart more horsepower. But, lest ye forget, bypassing the muffler doth make for a noisy car -- one that yon policemen might pull over for violations.