2003 Grand Marquis problems

[Adam]

So after sitting for about a month, I started it up again and it ran fine. I did check each of the coils by seeing if they produced an arc holding them up to the block and they all did, but it was running well then.

But after driving it back and forth to Milwaukee two days in a row, it started acting up on the way home today. Once the check engine light came on, I pulled into an Autozone, and had then put the code checker on it. It said misfire at cyl #2, which was (at first) surprising to me as it wasn't one of the ones that had one of the dirtier plugs when I pulled them. But I thought to look up how they number the cylinders to be sure, and they do it differently than how I learned it and #2 (which I would have called #4) is the one that had the dirtiest spark plug.

Now I looked and I can buy all 8 of the coils on ebay for less than I could get 1 for the price they were selling them at at the Autozone. Is this one of those things where the cheapies work just as good, or is there a real difference in quality? Also is there any benefit to changing all 8, or am I unlikely to see any others go bad in the future anyway?