I had a issue with my BMW e46 320D . It was losing power and had black smoke . After problems investigation I was focused on Turbocharger Pressure transducer or so called Turbocharger regulator, it’s purpose is to control an vacuum actuator valve which control on the other hand the geometry of the turbocharger! In case of over pressure boost of turbocharger, engine is going in emergency mode, that could be due many reasons, but at the end of the day, in my case I found that I have faulty turbocharger pressure transducer. You can see my maintenance in the video below 👇 👇 👇 .