The ECU pulls throttle and retards timing. No error unless there is a problem it identifies but overboost is a normal part of operation in some circumstances.
The power off then on is the throttle being hijacked on you. It's attempting boost control that it cannot do via the solenoid so I'd be looking at the boost behaviour next and see if there are actuator, solenoid or BOV issues. Check the control hoses too.
The brass butterflies actually gouge the body and create that ridge. As the calipers close and hit the gouged part of the body, a large gulp of air, that outlines an improper fuel mixture, goes into the engine, thus emitting the dreaded Solex hesitation. Often, this is made worse by the wear of the only shaft bushings that have allowed the shafts to reduced improperly, thus compounding the problem.
2016 Mercedes Benz CLA 250 Full Review, Start Up, Exhaust