1998 Mazda 626 Fuel Pump? TPS? Stutter.

My daughter has a 98 626 with the 2.5L V6. When driving it likes to hesitate or stutter. This only under constant speed when accel and decel it doesn't seem to do it. It has gotten worse in the last week and if you run down the highway with the cruise at 80 it's not so bad. Try to hold it to 60 and it will buck and stutter in not a rythmic way. It just does it here and there. Not only that, it runs out of gas at 1/4 tank on the gauge. At first I was thinking TPS (Throttle Position Sensor) or Idle Corntol Unit. Now I am thinking fuel filter. With all of these being way over 100 clams I would like to see what you guys think. I have tuned up and checked MAF as far as it being clean. I have also notice that when it stutters the tach niddle does not drop for that split second so I am not thinking electrical. We did run codes on it and found a O2 sensor fault but I am wondering if I am getting that once in awhile because of the stalling?