This rates as a "bad" interesting discovery. Last evening I saw something dangling below my diffuser. It turned out to be some anti corrosion foam sprayed on around the outer edges of the battery box. That was annoying enough; but the subsequent discoveries are aggravating and mysterious; so far, without answers.
Here's what a spanking new battery box below a GT2 looks like:

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I've now, today, discovered what it is supposed to look like. Notice the grommet and the extended "plug" (the black end turns but does not come off that I can see; and what is for, who in the heck knows and can tell me??).
And here's what mine looks like:
Clearly we have a different "arrangement" here! Ya think!? First off, what is that black spray paint about!? Clearly it was there before any of this crap happened (whatever that crap was, where, when and WHO did this): look at the three large and two small scrapes in the black paint? Shiny and new. This must have occurred since winter ended. I've been to "my" dealer service department twice since then: once in March and in the middle of April. Could have happened then. It is a backing up accident. We know this because of the direction of the scrapes: two parallel ones with the far lateral one. There is no way to make those marks going forward: because the rest of the undercarriage and exhaust pipes are lower than the bottom of the battery box.
So, if you like, have at it and theorize for me: how did this happen? And who would spray black paint on the battery box bottom, and why; and when could that have happened? The paint has nada to do with the damage, which occurred since the black spray paint was applied.
Finally, what is that low hanging "plug" thingie for? Anybody?