3) Exhaust pipe. Just change the muffler will not increase the car's power performance much more, but if replace the whole exhaust pipe for a high performance model, it will play a big role to the power promotion (especially after engine modification). The performance exhaust pipe is larger in diameter, more smooth the inner wall, smaller the curvature than the original, so that these designs can make the engine waste gas through smoothly at high speed, significantly enhance the exhaust efficiency. It should be noted that, too large of the blind exhaust pipe diameter will affect the exhaust back pressure and cool the gases down quickly. In general, if the engine has not been modified significantly, then the naturally aspirated engine which displacement is less than 2L, its exhaust pipe diameter should not exceed 50mmm, and 2L turbocharged engine exhaust pipe diameter also should be 70 ~ 80mm .

There is no necessary to replace the middle exhaust pipe separately, or you need to change the muffler together. Middle of the exhaust pipe is the cheapest in the system, but with the three-way catalytic converter, the price will be increased.
4) Muffler. Muffler is easily to assemble. High-grade muffler made by stainless steel (or even titanium), the modified muffler is lighter, more durable and more beautiful than the original. Muffler can be divided broadly into two types: the first is by the way of using staggered baffle caused the reflected wave to reduce the volume, the original muffler almost all of this type. The advantage is low cost and good silencing effect, the disadvantage is heavy and the large exhaust resistance. The second is common for high-performance models, with sound-absorbing material such as glass wool. The advantages are small limiting, light weight and the disadvantage is low muffling effect. Therefore, there is greater exhaust sound generally, but there is no direct relationship between the size of the exhaust noise and the engine performance. In addition, the diameter of the muffler exhaust port must meet the diameter of the front end exhaust pipe, it will not have much practical effect if it is too large.