I will try to make a quick guess.
You say that ALL you did was to replace the 6 plugs.. okay.. agreed..
Have you ever changed your plug wires? if not, then they may have begun to errode, and will conduct poorly.. Unless you know of a way to remove the 6 plugs without moving the wires at all, then I would imagine that you moved the wires. Having done so could have re-seated a few strands to make the idle run more smoothly..
I had a hesitation, stumble, and replaced the plugs... The problem went away, but, just as you said, by day 3 is was back.. I thought it was my new plugs (just as you do) but, when OBSERVING things, I started looking at my wires.. replace with Ford 9mm wires.. and the problem will go away.. there is nothing wrong with the OEM style plugs...
Just a little note, to say that YES. its possible that something else is wrong, even if you *only* change the plugs...
Ray
