After chasing AB days and nights for written explanation as agreed, this is what I finally received:
"Dear Mr. Kasio,
My apology for the late reply.
I understand your disappointment and hope that you would allow us the opportunity to address this matter to your satisfaction.
Please find the service record for your recent visit as follow:-
a. Service- Standard Scope
b. Replaced Engine oil & Brake fluid
c. Performance vehicle diagnose- Test Module
d. Check electrical / electronic system- function of the control units & sensor.
e. Check function of Digit AL Motor electronic (DME)
f. Check fuel pressure (fuel tank to high pressure pump)
g. Check high pressure pump and pressure regulator.( high pressure ready below spec)
h. Check battery charging with battery tester.(Re-charge)
Mr. Kasio, thank you once again for your patience and understanding. Please do not hesitate to contact me if you need further clarification on the above."
For whatever AB meant with the above explanation, I think I just take them at face value and have the car double-checked by other BMW specialist as I am now convinced they already did their "best". Yes, that's the best they could do, if you know what I mean..
and I do not intend to pursue this matter any further with AB..
The most important think to me now is the car runs as smooth as a 2004 530D could do, and swirl flaps removal will be next in the pipeline....