BMW Z3 M Roadster
The BMW M Roadster was designed to be the performance version of the BMW Z3, and there were significant differences between the two variants. The body of the M had many slight differences. These included front and rear bumpers, gills, rear wings, boot and mirrors.
Under the skin many of the components were beefed up with many of them taken from the E30 M3 and E36 M3 Evo including brakes and much of the suspension. The M could run a wider track under the flared wheel arches as well as wider wheels and tires to try to tame the increased power. The low offset of the rear wheels allows plenty of flexibility to increase the rear tire width. A dual exhaust system fed each set of three cylinders to two dual tailpipes. This quad exhaust has since become an BMW M division signature. Other changes included adding a limited slip differential, a different gearbox and strengthening the chassis.
The interior had a different look to the standard Z3, starting with the M-version steering wheel and including different instrumentation such as an oil temperature gauge. Finally, the car was available in M-specific colors which were not released for the regular Z3.
Source: Wikipedia, 2012