2001 Dodge Caravan 3.3 runs rough and hesitates

My 2001 Dodge Grand Caravan Sport 3.3 runs rough until itís warmed up and there is hesitation sometimes even after it is warmed up. This began happening right after filling up one day. I changed the plugs,
which were very dirty (carbon fouled) and the air cleaner and I ran a can of injector cleaner through it. There is also carbon in the exhaust (black spot on driveway under tailpipe). I know this indicates a rich mixture and my inclination is o2 sensor. Anybody have any other ideas? Could a clogged fuel filter cause this?
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