Since I am going to add the finned diffuser I have decided to do the following
order the Matte Black bumper Trim that is required. order the center piece with the fins.. (not the Carbon fiber Piece)
Have the Matte Black Pieces painted Gloss Black and Install.
once I turn in the car I will remove and sell the gloss black pieces and re-install the stock trim
I think the Gloss Black will go good with the Carbon trunk Spoiler and since the Side fins and front Grill are Gloss Black I wanted to keep it all the same rather than having Matte Black on the rear