so about a few days ago I've noticed that my air fuel ratio meter doesn't bounce around as much or a frequently as it did a few weeks ago. In fact my car seems to appear (according to the meter that is) to run slightly above the ideal stoich range and when I'm letting off the throttle it goes rich and then leans out. At light throttle instead of the meter bouncing around back and forth like it should (Its an autometer a/f ratio meter) it goes lean while going up hills! I don't ever remember it doing that before and my o2 sensor is a new Bosch one that I just replaced maybe this past october.

There is no check engine light, performance is good and my fuel mileage I think is the same. Interestingly enough this seemed to all happen when I changed my fuel filter out and noticed that I gained a noticable amount of power/throttle response.

Could this somehow be related? My car is stock OBD 0 but reset the ecu anyways by disconnecting the battery to do some other work to the car.

Suggestions anyone?
Thanks