1996 Toyota Avalon excessive fuel consumption

I did a tune up to my car and the now its eating up way to much more gas than usual. There is no leak in the fuel line. I've noticed that the acceleration is not as quick, sort of a dull pick up when doing normal accelerating. The car is due for a emissions test and I'm wondering if the car would fail inspection because of this.

I'm guessing the o2 sensor is bad or there is a vacume leak somewhere so should I just go and and get an engine computer diagnostics check just to be sure?