Make sure to change the cap and rotor also. If the plugs were in bad shape, chances are so are the cap and rotor. Also, on a 14 year old vehicle if you've never changed the plug wires, now is the time.
If that doesn't fix it, I'd suspect the O2 sensor. When they fail the mixture gets really rich. Is the inside of your tailpipe wet and greasy? Were your plugs the same? Too rich.