have a Automatic 4.9 2wd63,000 original miles. seems to be missing during normal acceleration and at any constant cruising speed Also engine runs rough and dies when initially started, does this once or twice then idles fine. went on a long 2,500 mile trip and was getting 12-13 miles per gallon. Replaced plugs, wires, cap, rotor, fuel filter, airfilter, oil change, oil filter, and ran 2 cans of seafoam through it and still hasnt fixed my problem.No warning lights. I unplugged EGR to see if that would help (something a buddy told me to try), no change, except check engine light came on, goes back out when plugged back in. I hope someone has experienced a similar situation and can give me some advice.
Thanks

 

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