Exhaust systems differ greatly from vehicle to vehicle. In an exhaust system where a single part performs multiple tasks, such as a manifold catalytic convertor front pipe, the system can be quite simple, with as few as 3 components.
However, for larger vehicles, especially diesel ones or more performance-oriented vehicles, systems can be far more complex. On such vehicles, there could be in the region of 8 components that make up the full exhaust system; and that is excluding sensors within the catalytic converters (CATs) and diesel particulate filters (DPFs), of which there could be four in total, taking the component count to around 12.