Ok, I managed to take pictures of the video screen. The hash mark I was speaking off can be seen on the right side of the screen. I know the pic isn't the best, but you can see this mark and it is horizontal. Also I took a pic. of the piston when it was further up the cylinder. Literally half of the piston has carbon on it and the other half is clean. None of the other pistons looked like this.

Any ideas?

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1999 MB SL500 (110,000 mi)
2004 Volvo V70 2.5T (220,000 mi)
2014 Tesla Model S 85 (136,000 mi)
MBCA member