ARM Downpipes For 2015+ Mercedes AMG GT, GTS, GTC, GTR 4.0L C190The ARM AMG GT C190 3. 5" Downpipes are engineered to remove these limitations and unlock the true performance potential of the 4. 0L M178 twin turbo V8. By dramatically improving exhaust flow directly after the turbochargers, these downpipes deliver faster spool, sharper throttle response, and substantial horsepower and torque gains when paired with tuning. The factory AMG GT downpipes are highly restrictive, designed primarily for economy and noise