Mercedes GT Roadster Engine Trouble

That sounds unpleasant. Besides the check engine light, stalling, and reduced power, is it struggling to start? Since you suspect the fuel regulator, have you checked the fuel filter? It's a simpler fix, and a clogged filter might be starving the engine. Could it be bad gasoline?

Thanks! It starts fine, thankfully. I hadn't thought about the fuel filter. Can I check that myself, or do I need special tools? How can I reliably test the gasoline? I usually fill up at the same station, but you never know.

Given the symptoms and mileage, a faulty fuel regulator or a defective high pressure fuel pump seems plausible. Checking the fuel filter is a good idea, but with those symptoms, engine misfire and rough idling, a professional diagnosis might be best. It could save you a headache, especially with the check engine light on. Taking it to a trusted mechanic might be wise.

You were right. The mechanic confirmed a defective fuel volume regulator. The high pressure pump was the problem. The repair cost was almost exactly as estimated, 1510€. Thanks for confirming my suspicions! At least I was prepared. I appreciate the advice.