Mine arrived primed, it was painted at the dealer.
Make sure to order also the stickers, they have different Part Numbers than the diffuser. My dealer forgot to order them and only realized when the diffuser arrived. Received them two weeks after the install.
'11 E92 BSM 335i / Saddle Brown Dakota Leather / M Sport / 19" 225M / DCT / Navi Pro / BMW Individual High End Audio System / Cobb Stage 2+ / AR Design Catted DP / ETS FMIC & Charge Pipe / K&N Drop In / BMW Performance Suspension / BMW Performance Diffuser / M3 Lip Spoiler