High flow secondaries. There is actually another guy on here (jzbm3) that has it already mounted.
OT, how is the GC sleeve kit holding up?
08 E90 | Jet Black / Black | 6MT
Mods: RAC RG63 w/ Pirelli Corsa 255F/285R | Akrapovic Evo Exhaust | OEM Blacklines
Winter Setup: OEM 18s w/ Nokian Hakkapeliita R 245/40-18