Use a high quality automotive polish and then finish off with carnuba wax to take out the scuffs and make the back of your Model X seats look as good as new. I do this with my $70K polished ebony grand piano and it works great. (I learned this from a guy that refinishes pianos for many of the orchestras here in Los Angeles) Please test the technique and waxes on a small area first to get the hang of it. Meguiar's makes some of the best polishes while "Beauty Shine Blue Carnauba 418" is the very best paste wax you can get. Make sure you slowly and softly buff the plastic with the paste wax at the end. Check out Youtube videos to learn the technique and use very soft, cotton towels to make your black plastic look great again.