The article deals with the subject of the impact of an exhaust system on the power of the internal combustion engine. In particular the article shows the possibility of increasing a power of the gasoline drive unit, interfering only with an exhaust system. The purpose of the tests carried out is to compare the results of measurements from the chassis dynamometer before and after the modification, and additionally to perform simulations for the key parts of the system in terms of shaping the power and torque curves. The analysis includes a simulation model of the exhaust gas flow through the serial manifold and also the sport manifold, especially the pressure distribution and the course of the velocity vectors at the characteristic points of the element. Before obtaining the final results of power measurements on the sport units, the roughness of the steel from which the collectors were made was also measured. The final stage is the measurement of power on the new exhaust system. The obtained results of power measurements and simulations were presented in the form of a summary, which focused on the impact of individual fluid mechanics phenomena on the formation of power and torque curves and detailing the advantage of the new exhaust system in comparison with factory system in terms of increasing the performance of the tested vehicle.