Duplex stainless-steel exhaust system with 1 × 90 mm outlets on the left and right for Volvo S60 II/V60 T3/T4/T5/T6, 2 + 4WD, type F — TA Technix

A complete exhaust system replaces everything downstream of the catalytic converter. Its main effect is acoustic: less baffled mufflers, a more pronounced low-end tone, and a more pronounced sound as the revs rise. As for 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 advertised 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 the original aluminized-steel exhaust. On a car you plan to keep, it is the part you only install once.