Ran some tests....
Pulled out the MAS, and jumpered the fuel pumps.

Fuel output is good. I tested it at 1.2L in 40 sec, however doing the same test I did last week I can get no output from the fuel lines after pushing down the air flap.

What is also interesting is that measuring the duty cycle with ignition on, I get 69.9% which is correct, but when I pushed down the air flap before it changed, and now it does not...
Could this be the OVP?

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2009 Mercedes ML320 Bluetec