Z4... DFI sounds just the same. There's just a lot more sound deadening material under the hood. Lift it up and stick your head under there. You'll hear it there, too.
Did nobody test drive and check this car out before buying? If it wasn't a corcern then, why such a big deal now? I think it's a symptem of spending too much time in the Faults and Fixes forum, myself.
