2000 Ford Explorer

Engine Performance problem
2000 Ford Explorer 6 cyl Four Wheel Drive Automatic 115000 miles

My 2000 Ford Explorer started chugging or missing while driving. It appears to be idling fine while in park but starts to run rough when put in drive. After I drive off and accelerate it runs real rough but will periodically appear to " catch" and increase power for a short second or two without having to push the gas pedal down anymore. That only lasts a second or two and goes right back to running rough. I tried to put 93 octane gas and some fuel injection cleaner in it but that hasn't helped. Thanks for any help I can get.
July 28, 2010.

Inspect and test all the following listed below: Oxygen sensor.
Catalytic converter.
Fuel injectors dirty/sticking.
Mass airflow sensor/Airflow meter.
Throttle position sensor.
Manifold absolute pressure sensor.
EGR Valve
Fuel pressure regulator leaking, fuel filter or defective fuel pump.
False air leakage.
Fuel contamination.
Foul/defective spark plugs.
Open spark plug wires.
Ignition coil/Coil packs defective.
Incorrect ignition timing.
Cap and rotor.

Note: If it doesn't apply disregard.

Jul 28, 2010.
I took it in today to have a mechanic look at it and he said the number 6 cyl. Isn't firing. He's not sure why yet. He said he's moved wires and plugs around but hasn't pin pointed it yet. Do you have any thoughts?

Jul 29, 2010.
P0306: Check no.6 sparkplug/wire/compression and injector

Jul 29, 2010.