Motor control light / workshop tip Frankfurt am Main

Hello together, at my V70 the engine control light has been burning for two months after I was put on with the car. As it happened on vacation, I called the ADAC. They sent a mechanic over, we looked at the car from below. There were no serious damage. At home I looked again with a friend and we discover a bigger crack in the Krummer. So cast manifolds exchanged for steel manifolds including cat. Light continues to burn. Does anyone have an idea what else that could be? Lambasonde? And a second question: Since the mechanic could not read the car on vacation anymore, I am looking for a good workshop in Frankfurt am Main. Someone a tip? Thanks and greetings