2 × 76 mm stainless steel exhaust system for BMW 3 Series E36 325i — TA Technix

A complete exhaust system replaces everything downstream of the catalytic converter. Its main effect is sound: less baffled mufflers, a more pronounced low tone, and a sharper-sounding increase 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 - the catalytic converter and downpipe.

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