Having reached a dead end resolving the meaning of the standardised OBD fault code P3263 I decided that, since my car was with the dealer, I would take advantage of the opportunity and pay for an official BMW diagnostic. This returned their code of 3FF0.
To my satisfaction this also pointed to an air flow problem and the advice was to look at two possible reasons. The simplest was the air mass air flow meter and the second was coking up of the cylinder head. However, the latter being rare on my car but more common when the engine is fitted in an X3. A strange occurrence but a relief since a decoke would be a very expensive fault to remedy. However, determining if a decoke was necessary would mean I would have to remove the inlet manifold for a closer look at the air ways.
