Assuming that both car are running in perfect condition, the SR will get better mileage. Injector size has nothing to do with fuel economy. I went to trade cars with my brother, so we met in Valdosta with both of us traveling 250miles. I have a stock KA with all maintenance done, and he has an SR with 2871r, 550's, and Enthalpy tune. The SR got 29 mpg. The KA got 26. Both doing 80mph with no stops. How much more of a direct comparison do you want?