BMW 2002 X5 - SES indicator on, with 227, 228 (mixture deviation) and 19 error codes

[leonid]

I have "Service Engine Soon" light coming up on 2002 BMW X5 X3,
with three error codes -
19 Activation VANOS inlet valve
227 Mixture Deviation : bank 1
228 Mixture Deviation : bank 2

Anyone had this combination, what parts are the prime suspects to be replaces?
I guess 227/228 may point to the intake system leaks, not sure how 19 relates...

If I clear the codes, SES light goes away but re-appears with the same codes after 10-30 miles of driving. No signs of engine under-performing. The problem started to happen after the service on power steering pressure/suction hoses and gasket, and valve cover gasket - but this may be just a coincidence.

Thanks in advance!
Leonid