How does the fuel mileage of the Corolla XRS compare with other Corolla models?
The EPA estimates that Corollas equipped with a five-speed manual transmission will get 32 mpg in the city and 41 mpg on the highway. Those ratings drop to 30 mpg in city and 38 mpg on the highway with the four-speed automatic transmission. Those numbers are significantly higher than the estimated 26/34 (city/highway) ratings for the Corolla XRS.

To what extent have Toyota engineers "detuned" the Celica GT-S engine?
When used in the Celica GT-S, the 1.8-liter motor cranks out 180 horsepower and 130 lb.-ft. of torque. That translates to a loss of ten horsepower and three pound-feet of torque when planted in the Corolla XRS.