Fans of BMW performance had two events to keep an eye on this weekend: the reveal of the M4 Concept at Pebble Beach, and the efforts of the Bavarian automaker's DTM teams at the Nurburgring.

The E34 M5 built between 1988 and 1995, however, is arguably truer to BMW's original spirit because of its inline-six engine. And whereas the original E28 M5 took the engine out of the M1 and ...