Mercedes E Klasse engine issue

Those symptoms do sound like a boost pressure problem. A faulty wastegate could be the cause. Have you checked the intercooler and its pipes for leaks or damage? That could also cause similar issues.

Thanks for the quick reply. What's the best way to check the intercooler and piping for leaks? I want to make sure I check it properly.

Start with a visual check. Look for any physical damage like cracks or holes. Check the connections and hoses to see if they're loose or worn. If you don't see anything, a smoke test is a good way to find even small leaks. If you can't do a smoke test yourself, a mechanic can help diagnose it. Since the wastegate, throttle body, and boost control system might be involved, a professional diagnosis is a good idea.

Thanks for the advice. I took it to a shop, and they confirmed it was a bad wastegate, like I thought. The repair cost 860€ for parts and labor. Thanks again for the help.