This is the OEM EVAP Purge valve located on the EVAP (Charcoal) canister in the rear of your Q50.
The purge valve is part of the EVAP (Evaporative Emissions) control system. The job of this valve is to prevent fuel vaports from the gas tank from escaping into the air. Under certain conditions while the engine is running the fuel vapors are purged from the charcoal / EVAP canister at the rear of the vehicle and burned inside of the engine. Overtime the solenoid in these valves stick or fail, resulting in CEL Illumination (common codes: P0444, P0445) and rough running.