Not bad at all considering the 560 crank horsepower rating for the 991 Turbo S. Keep in mind this was a Mustang dyno which will read more conservatively than a Dynojet. It will be interesting to see some all wheel drive Dynojet numbers for comparison but this car is likely putting out over 500 wheel horsepower stock on the Dynojet.
Comparing these results shows the 991 Turbo S is stronger than the 997.2 Turbo S PDK but not by as much as one would think. The difference seems to be roughly ~30 wheel horsepower. With more runs we will have a better idea but the 991 is very, very efficient.