Since you already have Stillen CBE and CAI, get some Berk or Stillen HFC's to add more louder sound and power. Also, you can get Stillen Headers too
As for headlights, my plans when I get my Z, I'm going to change out the HID bulbs to 6000k's. You can do that and maybe, do some black housing touch-up for your headlights. Contact 180 degrees place for headlights and LED's you can do.
Get some nice wheels too lol. Those are my suggestions!