2003 Ford Ranger

Engine Performance problem
2003 Ford Ranger 6 cyl Two Wheel Drive Automatic 41000 miles

2003 ford ranger with 41000 miles. Bought truck from an individual had 26000 miles, engine idles rough, it has since I bought it. It has a dead miss at about 80-85 miles per hour. Somebody fooled with plug wires. I changed plugs and air cleaner. Checked for vacum leak. Did not find any. What do you think?
July 20, 2010.

Engine running rough or misfiring can be cause by the following: 1. Defective spark plug
2. Inadequate spark/coil, defective spark plug wire.
3. Lack of compression
4. False air leakage.
5. Faulty fuel injectors.
6. Insufficient fuel pressure.
7. Contaminated fuel.
8. EGR valve that is leaking.
9. Oxygen sensors.
10. Throttle position sensor.
11. Idle air control valve.

Jul 21, 2010.