[dimsum.dumdum]

First off... Lets give a full part number list of all the BMW OEM part numbers I purchased:

51 19 2 455 832 Front attachment, black
51 19 2 455 835 Pro carbon front attachment, left
51 19 2 455 836 Pro carbon front attachment, right
51 19 2 455 897 High gloss black sill add-on section, left
51 19 2 455 896 High gloss black sill add-on section, right
51 19 2 458 369 Carbon rear spoiler
51 19 2 455 859 High gloss black rear bumper trim
51 12 2 455 862 High gloss rear towing eyelet cover
51 19 2 455 819 Carbon rear diffuser
OR OR OR
51 19 2 455 740 Carbon rear diffuser
12x Part No. 7 002 953 - Expanding rivet
4x Part No. 7 133 553 - Screws

The rear diffuser you buy will depend on whether you have the hands-free trunk foot kick feature available with the executive package. I do not so my part number was 51 19 2 455 819 - Check with your dealer or supplier on which one you need.
You can also refer to the attached guide that I found. My body guy was very thankful for this.

Here are the PICs