Yes I did ensure that I retarded the cam adjuster.

The cams are set on the 280 version as per the dowel holes drilled into the back of the cam gear sprocket wheels. However, the AMG valve openings are advanced by 6 deg for the inlet and 2.5 deg for the exhaust.

That advance could be achieved by a new cam profile for the inlet camshaft (it is an AMG specific cam part number). It could also be achieved by advancing the sprocket gear one or two teeth.

But how do they achieve 2.5 deg advance for the exhaust for the exhaust cam which is identical to the 280 engine? Could that be achieved by the higher compression (shaved) head alone, or shaved head and advance one tooth?