I have a 1999 cav with a 2.2l I4, auto tranny, and 15gal fuel tank. my car is only getting 12-14 miles to the gallon, I did a complete tune up on it and it hasn't changed i even replaced a bad O2 sensor. plus there are the occasional times that i push the gas pedal all the way to the floor and the car will roll slowly forward like i'm feather footing it and then after about 30 secs to 1 min the car will roar to life and accelerate like it should have to begin with. I could really use some advice on this.
thanks everyone

youre cat might be clogged