7.3 what do you think it could be

[J. Wheeler]

help me out here guys/gals.
My 03 has developed a problem. It starts fine and runs good at first. I can drive it all day with no problems but if i park it or sit at a light for more than a few minutes it starts to miss intermittently. The longer it sits the worse it gets. I can rev it up and it clears out for a moment. and it still pulls fine up hills. I checked codes. only one came up for a bad sensor in the air filter box. no Engine light, no strange smoke, it started right after i changed the oil. ( which is kinda bothering me)
Any knowledge you have that may be able to help me would be greatly appreciated.

[J. Wheeler]

any thoughts?

[boosted-wreacker]

clean out fuel filter cup and new filter