We have a winner! As suggested I measured the distance to the top of the plug in cylinder 1 and in cylinder 5 and there is an inch difference. Here is a link where you can see some extensions.
https://www.autozone.com/ignition-tune-up-and-routine-maintenance/spark-plug-non-fouler
Why was it installed? No idea... but if it ain't broke don't fix it. I might mention that I paid $5,000 for this Boxster, so I plan to enjoy it rather than find unnecessary work to do on it.

The coil pack sits 1" proud of the head?
That would not be good.

I was wondering the same thing..:rolleyes:

If this thing is screwed into the cylinder head’s spark plug threads, is there an easy way to unscrew it without removing the head? Seems like it could be risky to try.

Bend the tip of a coat hanger and see if you can get it to move?

Is there a hex end sticking outside the plug hole?

Does it ever blink ??

You really should get that out of there. As mentioned, having the coil pack stick out an inch is not a good thing.

It would seem that I am somewhat cautious about how to handle this anomaly.
My analysis is:
1) the engine ran well as it is.
2) someone made a conscious decision to install the extension for a reason… that I have no way of understanding.
3) simply removing the extension would, I assume, bring me back to the problem that lead to the installation of the extension.
4) so why do anything? At the very best removing the extension could lead to the engine running well… which it does now, but, at worst, it could lead to a problem that means removal of the engine for repair of the original problem.

Here is my latest take on the situation…
I doubt that the original problem was plug fouling, simply because there is no visible evidence (oil or carbon in the extension or different colour of deposits on the spark plug). The only other reason I can think of is that someone damaged the threads in the spark plug hole and installed the extension (perhaps with JB weld or some-such) so that plugs could be changed without further deterioration of the original threads. Remember that this is in the cylinder that is the most difficult to access, so chances of cross-threading are maximized. If this is the case trying to remove the extension would mean having to remove the engine to fix the threads. Perhaps I am wrong, but who wants to take a chance? Not me.

The installation of the coil pack isn’t a problem, I will fabricate spacers so that the mounting screws aren’t putting pressure on the “ears” of the pack. But again there was no problem before.

it's not a head-off job to remove it, but probably a cam cover off job (and all the reqd cam holding tools) unless you got skilz and can dr. longskinnyfinger it out through the little hole in the cam cover. hack way to do a thread repair. first step would be to confirm your thesis - get your borescope in there and try to see the hex head of the anti-fouler. then check to see how the coil pack sits - did you notice it sitting proud when you removed it? then think to yourself - whoever used an anti-fouler for thread repair also had my cam cover off - do i trust any other work he's done? personally,i'd pull the cam cover just to confirm, remove the fouler and repair the thread properly.

edit - i presume it would come out just like a spark plug, so not even a need to remove/inspect cam cover. not sure how hard it would be to put in a helicoil with all that in the way, however (just trying to manage all the shavings) ...

1) So?
2) Probably just a moron.
3) Who says there was ever a problem?
4) If you're going to do something, do it right (also an answer to #3).

Have fun with that. ;)

Before even getting to the coil pack being an inch higher than normal, what about the spark plug not being fully seated in the head? Spark plugs are meant to be threaded all the way into the head, and they have that compression washer and shoulder at the end of the threads to make a tight seal with the cylinder head. Seems like that would be an issue too.