I bought an intake when they were unloading them for about $250. It looks nice, and sounds nice, but my butt dyno doesn't notice much of a difference.
If you find one, the replacement filter is a Wix 46301, or NAPA 6301, same thing as Wix makes the NAPA filters., late ninety's Pontiac Grand Am, lol. It fits perfectly, similar pleat count. The BMW filter is $55, the Wix is under $10. I bought several, which ought to last a while.
12 BMW X5 3.5i xDrive (E70)
12 Audi A4 Quattro 2.0 turbo (the black sheep)
03 BMW 330i ZHP (E46)
01 BMW X5 3.0i (E53)
79 Triumph Spitfire
73 MGB