To get the most power out of an engine you disregard emissions standards, the manufacturer can't do that without getting fines and recall orders.
Depends on the car. See Supplemental Federal Test Procedure US06[0], required by the EPA for light-duty vehicle certification since 2007.
It is also largely irrelevant in the real world: nobody is going to tune a car to have mediocre part-throttle performance but then go all-out on full-throttle.
0 - https://www.epa.gov/vehicle-and-fuel-emissions-testing/dynam...