A complete exhaust system replaces everything downstream of the catalytic converter. Its main effect is acoustic: less-restricted mufflers, a more pronounced low tone, and a sharper-sounding rise in revs. In terms of power, the gain exists but remains modest on a stock engine, because the restriction in a production engine is mainly upstream - at the catalytic converter and downpipe.

The second effect, less often highlighted but more lasting, concerns weight and durability. A stainless steel system does not rust, can still be removed ten years from now, and weighs less than the original aluminized-steel exhaust. On a car you plan to keep, it is the part you only install once.