I drive like a granny right now on a stock FRS i get 29MPG in the city. I think i will get 1-2+ mpg when i do add a little power and still drive like a granny. Shifting @
2000-2500 RPM
You will get the same effect with a turbo. But you will be more tempted to step on the throttle. So when you drive agressively you will lose MPG