Mercedes SL Stalling and Low Power Issue

Whoa, that sounds rough! A faulty fuel regulator can definitely cause those symptoms. You mentioned fuel injection, so it's likely starving the engine for fuel at low RPMs, hence the stalling. The reduced power makes sense too. Have you noticed any engine misfire codes? If so, that's almost certainly fuel-related. Also, is the check engine light constant, or does it flash?

I did see some misfire codes when I scanned it, yeah. The check engine light is constant, not flashing. What exactly does the fuel regulator do? I'm still learning about this car maintenance stuff.

Okay, constant check engine light and misfires definitely point to fuel delivery problems. The fuel regulator basically controls the amount of fuel being delivered to the engine's fuel injection system. If it's not working right, the engine won't get the correct fuel-air mixture, leading to misfires, stalling, and power loss. Honestly, with those symptoms and the codes you're seeing, I'd recommend taking it to a qualified automotive repair shop. They can properly diagnose the high-pressure pump and confirm if the fuel volume regulator is indeed defective.

I took it to a shop, and you were right. It was the fuel volume regulator, and it looks like the high-pressure pump was indeed the issue. The automotive repair including labor and parts came out to around 1510€. At least now the engine runs smoothly and the check engine light is gone!