From what I know, for earlier model years, the car came w/o FM booster from the factory. Only if you complain about differential noise will they change to fluid w/ FM booster. For later model years they may have changed it from factory, but I cannot confirm.
2011 E92 M3 DCT
1991 Spec Miata
2008 E92 M3 DCT - KW Competition 2-way / Brembo 365 BBK / OMP ARS racing seats / rear seats delete / GT4 aero / AiM EVO4 data logger / SmartyCam racing camera
2008 E92 M3 6MT
2008 E92 335xi