Carbon direct intake kit for VW Golf VIII (CD) 1.4l Turbo — TA Technix

A direct-fit intake kit removes the airbox in favor of a short pipe and a cone filter. Two things change: airflow, because the airbox restrictions are removed, and intake noise, which becomes pronounced and very noticeable under load - often the real reason for buying one.

All the performance gain depends on air temperature. A filter installed in the engine bay draws in air at 60°C or more: it is less dense and cancels out what it was supposed to improve. Serious kits come with a heat shield and a cold-air intake; without one or the other, the gain is theoretical. Carbon conducts considerably less heat than aluminum.