RENNtech EVM | Exhaust Valve Module | 117-CLA 45 AMG; 156-GLA 45 AMG; 176-A 45 AMGRENNtech Exhaust Valve Module Permanently Open Exhaust Flaps. 117 CLA 45 AMG; 156 GLA 45 AMG; 176 A 45 AMG. SKU: EVM: 49. 117. 906. 40 NOT SO FUN FACT: If your Mercedes AMG is equipped with factory exhaust valves, with or without a center console button to open or close them, factory settings do NOT allow the flaps to fully open unless certain speed and or RPM have been reached. For example, while cruising the exhaust flaps will never fully open! THE