Ford Repair: misfire cylinder 3 & or 4, hesitation problem, high mileage

Question
1997 Ford Expedition 4.6 liter Automatic with air condition. It has 200,000 miles on it. Had a misfire on number 4 cylinder still having hesitation problem.  I have changed spark plugs and plug wires, now having misfire code on number 3 cylinder.  All sensors are within spec according to snap on scanner.  Still misfiring and surging at around 40-50 mph.  Check pcv valve and hose no apparent leaks that i can tell.  Misfires from starting position also. Other than this problem engine runs great lots of power otherwise.  Spark plugs looked a little lean. Is it something that the computer has to be reset because of the high miles?  I am completely stumped hope you can help.

Answer
Hello and thanks for the question...I'll try to help.
With that kind of high mileage..I would suggest a few things:
1. cylinder compression test
2. check the flow and condition of the fuel injectors
3. re-scan the computer system for values

Erik