I believe the REAL reason for the air pump is that the emission laws in the "Motherland" require testing within 60 seconds of starting the engine. Since the engine is cold (so the cold catalytic converter isn't doing anything yet) and the engine management system has the fuel mixture running rich, the air pump compensates for that brief period until the engine has warmed up. Then it is no longer in operation.

Here in the states, vehicle engines are allowed to warm up prior to testing, so the air pump is a moot issue.

__________________
2009 ML350 (106K) - Family vehicle
2001 CLK430 Cabriolet (80K) - Wife's car
2005 BMW 645CI (138K) - My daily driver
2016 Mustang (32K) - Daughter's car