There are several differences in the M54 after 02/2003. When was your car actually made?
The MAF is a 6 pin connector, the intake manifold does not have the air temperature sensor, the SAP uses a second MAF sensor to determine if the air pump is running.
There are also differences in the O2 sensors in the later M54 engines.
Up to 02/2003 the M54 used the MS 43 ECU, after it used a MS45 ECU.
Discounts on new and CPO cars.
Most Dealers offer a parts discount, BMP Design 10% off