OEM style CF Dual Diffuser $220 *great deal!* now 180!
Arkym CF Dual Diffuser. *sold*
OEM in matte black *sold*
pick up DT or Markham/RH.
335i Borla Exhaust. *sold*
looks dope and sounds like a beast. fits both i and xi. e90s may need some slight modifications from local muffler shop.
tons of youtube clips, here's one from titan: