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AMG GT Downpipe Guide — M178 4.0TT Catted vs Catless, HP Gains & What to Know
The Mercedes-AMG GT is a front-mid-engine grand tourer built around the M178 4.0-litre twin-turbo V8 — a hand-assembled unit that shares its displacement and hot-vee architecture with the C63’s M177 but differs significantly in its dry-sump lubrication, engine mounts, exhaust routing, and ECU calibration. The AMG GT’s factory exhaust system is designed with emissions compliance and NVH refinement as priorities, and the catalytic converters sitting directly downstream of each turbocharger are the primary flow restriction in the system. The Factory Exhaust Restriction In the AMG GT, both turbochargers sit inside the cylinder bank vee, feeding exhaust through tightly packaged catalytic...