Well, it depends on whom you ask.
For those familiar with their BMW M5 history, the E39 M5 is regarded as one of the greatest generations of that sport sedan. Everything about it, from its design and engine to overall refinement, was just right. The E39, built from 1998 until 2003, was powered by a 4.9-liter V8 that had an output of 394 horsepower. And unlike M5s (or nearly everything else from BMW today), the E39's sole gearbox was a six-speed manual. So was it even possible to make the E39 M5 better? Turns out it was.
California-based aftermarket tuner Dinan worked on a limited number of those M5s and created something even more phenomenal. With the help of a supercharger and other upgrades, its E39 M5 had an output of more than 620 ponies. Electric Federal caught up with one Dinan E39 M5 owner for his insight.