If you can, pick up this weeks edition of Autocar magazine out of England. They have a luxo sedan comparison with a BMW M5, Alpina B10, EV12, Lotus Carlton, and the 5.7 litre Opel I think. In the article it mentions that an M5 owner took the speed limiter off his car and ran it at 186mh for a few moments before the engine blew. Beware of this because the warranty will definitely not cover a rebuild.