G Klasse air intake problem Reduced power and rough running

Sounds familiar. I've got a G Klasse too and had similar symptoms. The hissing is a big clue, pointing to an air intake leak somewhere. The flap control system is designed to optimize air flow into the engine, especially at lower RPMs. When it malfunctions, it's like trying to breathe through a pinched straw. The engine light coming on confirms something is definitely amiss. Have you checked for any obvious cracks or loose connections in the air intake system yourself?

I appreciate the insight. I examined the air intake system but found nothing obvious. Can you elaborate on where exactly the flap control mechanism is located and how it might be inspected further?

The flap control is integrated within the intake manifold assembly itself. Accessing it usually requires removing the manifold. Without diagnostic equipment it's difficult to pinpoint the exact fault within the control system. Since you've already inspected the accessible air intake components and found nothing, I recommend a workshop visit. Their diagnostic tools can isolate the problem and confirm if it's indeed the intake manifold flap control. Continuing to drive with this issue could potentially cause further damage to the engine. Get the error codes read out.

Understood. I took it to a workshop. The diagnostic confirmed a defective intake manifold flap control switch. Repair cost was 465€. Thanks for your help.