Apart from the usual tire width, tire pressure, steering wheel diameter, and similar points, there were multiple power steering systems used on different vehicles at different times. Regular, Servotronic (variable assist based on vehicle speed), Active (variable steering ratio based on vehicle speed), and so on. I am not sure which specific systems came as standard and optional on each model and each year, but be aware that there are a host of possibilities when comparing two vehicles.

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2007 X3 3.0si, 6 MT, Premium, White

Retired:
2008 535i, 6 MT, M Sport, Premium, Space Grey
2003 X5 3.0 Steptronic, Premium, Titanium Silver
2002 325xi 5 MT, Steel Grey
2004 Z4 3.0 Premium, Sport, SMG, Maldives Blue