BMW N55 Downpipes Guide: Catless vs. High-Flow
The exhaust downpipe is the first part of the exhaust system on the N55 engine. It bolts-up straight to the turbocharger and passes air from the turbo to the cat-back portion of the full exhaust system. The OEM downpipes have catalytic converters on them, for emissions purposes. However, the catalytic converters are extremely restrictive and…