Exhaust manifold for Audi TT 3.2 VR6 (8N), VW Golf IV R32 (1J) — TA Technix

On a naturally aspirated engine, the manifold is the exhaust component that changes the engine's character the most, and the only one that works through pressure waves, not just flow. Equal-length tubes allow each cylinder to evacuate without interfering with the next one: cylinder filling improves, and with it, torque across a given rev range.

The design determines the power band: a 4-2-1 brings torque back into the mid-range, making it well suited to road use; a 4-1 shifts everything higher up and hollows out the low end, which only makes sense with a camshaft and exhaust system to match. A sport manifold installed on its own on a stock engine delivers a real but modest gain - it is a component that needs to be considered as part of a complete setup.