Is this something you just noticed after picking up the car? Have you measured left to right before? Doesn't BMW set suspension so the driver side is little higher than passenger side (higher when driver is not in the car) to compensate for the weight of the driver? But 3/4" seems too high though.

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2004 X5 4.4i
2001 E46 M3
1995 E34 525i
2008 Acura MDX
1984 Maserati
2011 997 Turbo