It's spray on rust proofing.
I had the same exact craptastic $h!t on my 2010.
I bought in, into the whole sales pitch from my dealership sales person, when I bought my SHO new.
It came along with undercoating, Scotch guarding the interior & something else which skips me at this moment.
IIRC, it was a lil over $1k for all of this post sales "service". I had to bring car back 3 days after I drove mine off the show floor.
When I got it back, the crap was everywhere..... door jambs, hinges, engine bay, shock/strut towers, you name it.
It was hideous. Sticky as all ****, collected dirt just as you described, turned black, my God what a fk'n mess.
I was ******.
I eventually used a combination of Xylene, a commercial grade wax/tar remover, & good old fashioned elbow grease combined with one of those "safe" scrub/sponge pads designed to remove bugs & crap from car's exterior.
It was a painstaking, several day process, but eventually I got it all removed.
Now, just like my fellow Mike posted (mval) I too show my SHO, I too am religious about cleaning/waxing these areas as well.
Proud to report, no issues in 6yrs of ownership, along with most all of those years seeing daily driven use here in good 'ol CHI-Town, the new ****** capital of the world.
Don't believe crap that Tech says, he/she is blowing donuts up your @$$ & is likely "trained" to go right along with the sales ploy/pitch from the sales dept. to help increase/pad the profit margin(s).
Steer way clear. Run the other direction.
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