Mercedes C Klasse Engine Power Loss

The symptoms you describe definitely point towards a boost pressure issue. A faulty vacuum switching valve is a plausible cause, as it directly affects the turbocharger's operation. A vacuum leak anywhere in the system controlling the turbo could also be the culprit. Have you checked the vacuum lines themselves for any cracks or disconnections? Turbo lag and compressor surge are common indicators of such problems. Regarding the intake manifold and pressure sensor, while they could contribute, they are less likely than a direct vacuum or valve issue. I would advise checking the pressure sensor output with an OBD scanner to see if the values are within range before suspecting the intake manifold. A faulty sensor can definitely trigger the check engine light and impact performance.

Thanks for the input. I haven't checked the vacuum lines myself. I'm not entirely sure where to start looking for a vacuum leak. Is there a common location where these leaks tend to occur on this engine? And about the OBD scanner, what kind of pressure sensor values should I be looking for, and where can I find the correct specs?

Vacuum leaks are common at connection points and along any rubber sections of the lines, especially near heat sources. Carefully inspect the lines connected to the turbocharger, vacuum switching valve, and intake manifold. You'll need to consult the Mercedes service manual for your specific engine to get the precise pressure sensor values. However, generally, you're looking for smooth and consistent readings that correspond to engine load. Erratic or out-of-range values indicate a sensor problem. Given the complexity, and if you are not comfortable with this, it would be best to take it to a workshop for diagnosis and repair. They can perform a smoke test to pinpoint any vacuum leaks and verify sensor functionality.

Thanks for the help. I took it to a workshop, and it turned out to be a faulty vacuum switching valve, just as you suspected. The repair, including the part and labor, came out to around 140€. The car is running much better now.