In the beginning, there was the engine, and lo, it did require fuel and air in its cylinders, which would combust when a spark was introduced. But alas, there was verily always some leftover stuff in the cylinder that needed to be cleared out via the exhaust system. The faster the exhaust could be pushed out of 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 keepeth our streets noise free and our air breathable.
But what if we promiseth to only bypass the exhaust system while we race safely on the track? Why, then we may installeth a Y-shaped exhaust cutout. It shall be inserted into the exhaust system between the engine and the muffler, with "the slant" (as the short pipe shall be known), facing downward and toward the back of the car. When extra horsepower hath been shown 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. Whilst on the streets of the town, the cutout can be cut off, allowing the exhaust to travel the full extent of the system, through catalyst and muffler alike.
Yea, verily, clearing out the exhaust more 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.