The most powerfull edition of the Z4 with the "M" badge has the current M3 3.2 litre engine with the 343 hp. New suspension settings, plus all the Z4 faeclift tweaks. 0-100 km/h in 5,0 sec, rival to the Porsche Boxster S.
The Z4 has had a mild facelift -(bumpers, lights etc) plus 2 new engines, 2.5 & 3.0 litres with 218 and 256 hp (from 192 & 232 respectively )