Complex sentence: The Saturn Curve was a roadster concept by Saturn (even if designed by the SAAB head of design Michael Mauer) that was shown at the 2004 North American International Auto Show along with the concept of Saturn Sky.
Split into simpler sentences: The Saturn Curve was a roadster concept by Saturn designed by the Michael Mauer which was the former head of design at Saab Automobile. It was shown at the 2004 North American International Auto Show along with the concept of Saturn Sky.