He also added 50 lbs of 93 octane fuel and ran the 0-60 with the extra weight. Only about 1.3% extra weight but the car was heavier with the 93 octane run.
I suspect the turbo is allowed to overboost a bit longer plus the additional ignition advance adds power and decreases 0-60 times. 2 to 4 10ths is a pretty big improvement.