I'm curious as to how a fuel filter needing replacement can cause the engine to run rich and get poor fuel mileage? It won't hurt to replace it (and the PCV) but it won't be your problem.

pull a plug or 2, they should be black (well, for this condition). normal condition is off white/slightly brown.

with 193K on the car...im betting the 02 will help your problems

Well it wouldnt cause it to run rich, but it could restrict fuel flow. i guess this would be more wear and tear on the pump rather than bad MPG, but i would still change it

I am going to take the car to the auto store and get a couple new parts, O2 sensor, pcv, and fuel filter. I will pull plugs after replacing these and let you know the results. Thanks all for the help and suggestions. Keep them coming in the meantime if anyone else knows of anything else. Thanks again. Bryan

DONT get a bosch o2.

What was the fuel mileage BEFORE you changed the plugs? Better? Worse? Same? Are your driving habits the same, or now that you have new plugs are you more impressed with the throttle response and you're now driving like my wife (two throttle positions - full on or full off)? LOL.

Mileage is about the same as before, maybe slightly better. Driving habits are comparably the same, maybe a few more full throttle pulls just to hear the whine

What is wrong with the Bosch sensor? Just wondering. Thanks Bryan

they dont seem to work well with our cars and fail early i believe.

Second on the Bosch sensor. I've had too many of these come back at work, often within months with the heater element burnt open (infinite resistance) every time.