After going through the various drive modes (Eco, Comf, Sport, Sport Plus), and the transmission options, (Drive, Sport, Manual), I discovered a dedicated Launch Mode indicated on the instrument panel. It's effective and cuts nearly a full second from acceleration times across the board without wheelspin. Also, I discovered the transmission short shifts in Drive in modes other than Sport or Sport Plus where it will upshift at the indicated redline rather than 500 rpm shy as in other modes. It also will hold gears (without upshifting) in Sport or Sport Plus. All that all said, what an engine! This should in no way be considered a consolation engine. There's plenty of grunt down low in the rev range and exhilarating power as the tachometer swings up toward the redline. Strange how in this application (4-door 428), it lacks the raspy intake/exhaust that the 2-door 428i had. Also, it's a few tenths slower across the board, but only 138 pounds (as tested) heavier.
Reasonably short and consistent stopping distances, near-zero reduction in effectiveness and high-thermal capacity. Modest nose dive but no wander or wiggle under full-panic stop simulation.
In contrast to the two-door 428i Coupe that was overflowing with confidence AND predictable handling at the limit, the four-door Gran Coupe matches the confidence, but lacks the predictability. I found I was "chasing" the car's responses rather than flowing with them. Steering weight was appropriate, response was crisp, but what the car did thereafter was not constant from cone to cone. Also, I found the throttle response to be less linear and more apt to surge which also made the car less predictable.