Collection: Mercedes Downpipes – Catless High-Flow TIG Welded Stainless Steel

On a stock tune, almost certainly. Removing the primary catalysts means the downstream oxygen sensors read differently than the ECU expects, and it logs a catalyst-efficiency fault. A matching ECU calibration resolves this properly at the software level. We do not use or recommend defeat devices.

The car will run without one, but you leave most of the gain unclaimed and you will likely have a lit dash. The downpipes open the exhaust side; the calibration is what lets the ECU actually use that extra flow. Most platforms here offer the tune as an option on the product page so the file is written around your exact hardware from day one, rather than paying for a re-flash later.

The front differential and driveshaft on a 4MATIC car occupy space the exhaust would otherwise run through, so the routing and bracketry differ even when the engine is identical. On the M157 E63 and CLS63 this is the single most common ordering mistake — same badge, same engine, different pipe. Check your drivetrain, not just your model.

Primary downpipes bolt directly to the turbo outlets, where the largest restriction sits — that is what most sets on this page replace. Secondary sections sit further downstream and replace the second set of catalysts. They address different parts of the system and can be run together for a full decat.

Often a 24″ O2 sensor extension harness. Catless pipes reposition the sensor bungs relative to the factory pipe and the original leads may not reach comfortably. Most Mercedes V8s need two. It is the cheapest part in the build and the one most likely to stall an install halfway through.