1996 Jeep Cherokee Intermittent missfire

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1996 Jeep Cherokee Four Wheel Drive Manual 160000 miles

1996 Jeep Cherokee 2.5L 4 cyl, engine has 15,000 miles. I have been having a weird intermittent missfire that seems to happen after it warmes up for a few minutes but is totally sporadic. It could be driving just fine then all of a sudden it starts to lose a little power. Then it will just drop out like its not getting fuel through the entire throttle range except wide open. The check engine light will come on with, up flow O2 sensor "running lean" code. After a few minutes or so of running it wide open it will clear up like it just had water in the gas or something, although I ran 2 tanks of gas with drygas through it. If I let it idle when its doing this it sounds like its hititing on 3 or so cylinders and slowly goes from normal idle rpm slowly down almost stalling untill the pcm kicks it back up to high idle.
I changed the fuel filter and it seemed to help in the slightest bit. My question is, do you think the sox filter on the pump could be pluged bad enough to make this happen? Like I said it doesnt do it all the time just sporadically, and the check engine light will go off by its self sometimes if its had a warm start and its not missfiring at the time.