Status Gruppe/AP/Fabspeed headers, and Evolve tune. Michelin Pilot SuperSports.
Forget an intake (unless CSL/Evolve airbox), forget the elbow, forget the drop in filter. You'll have a better time taking your woman out with that money. There are some gains to be had with intake scoops, and underdrive pulleys.
This is ALL assuming the maintenance is up to date.
2001 M3, LSB 6spd, purchased 6/09 with 25K miles.
Mods: Coyne Performance built ///M3