Munich has no plans to launch an M version of the new two-seat hardtop. This has disappointed fans of the BMW Z4.  The highest power of Z4 is 225kW (306hp) which may be increased to 245kW (333hp) if BMW Motor sport kit is brought in for the model.
Günther Manhart who is the founder of the tuner has 25 years of making over BMW engines has adapted the V10 naturally drew out engine from the M5 and M6 into the tiny and slender body of the Z4. Equipping such a monster power plant showed an agonizing challenge. But the owner of the tuner overcame this at last. Now it is seated just over the car’s front axle. The aggregate kerb weight is 1,450kg.
Factory power at present is 373kW (507hp) which Manhart has altered to 405kW (550hp) by reworking the ECU. Performance has become very strong with the 0 – 100km/h dash attainable in 3.9 seconds. They have also got rid of the 250km/h speed limit.
Other changes include an AC Schnitzer stainless steel expel system with 4 muffler tips, a new M5 E60 6-speed physical transmission system which includes a Fichtel & Sachs clutch and a M5 E60 differential.

Source and more images on: World Car Fans