[Racer20]

I'm convinced that chassis dyno tests performed by aftermarket companies are quickly becoming obsolete.

The VW diesel scandal showed the challenges: the ECU recognized that it was in the dyno and ran a different calibration.

I believe that so many factors are taken into consideration today that a cars power output cannot be measured simply and assumed to be consistent and representative on a dyno.

For example, maybe this M5 wasn't getting enough cooling air and dialed the tune back. Maybe the car detected some conflicts between various sensors because it wasn't actually moving.