I have the fuel pressure regulator with a little larger crank pulley and a K&N air filter. nothing else changed from factory (engine). It is the same engine on the SLK, exactly the same (except SLK can have manual trannies, and an electric fan instead of viscous coupling one, and battery in the engine compartment...)

I appreciate your help. I will ask the guys at the dealer wednesday to maybe check more than just the shut off valve itself. Maybe it's effectively the shut off valve that fails, but then there is something that makes it fail.

And the shut off valve is not under warranty, fortunately, they don't charge is it's the same part that fails since it's like on the part's warranty. They might charge diagnostic time.

What is really bugging me is why does it fail after 6 months, not after like 3 days...

Etienne