WOW. As a consolation, have you considered that carbon will turn into diamonds with some heat and pressure....
Before spending that kind of money on carbon built-up in such a new car, I'd:
1) Look for a second and third opinion.
2) try a heavy dose of fuel injector cleaner. (direct injection, in addition to through the gas tank)
3) Change oil for a very high detergent type
4) Try an engine flush
Good luck
jackD