I am assuming you mean this (see attached photo)
Dunno what's it called, but there used to be a few companies, which made hi-flow replacements; the only one that I am still aware of is around is AFE.
Google "AFE intake Boxster" and you shall find.
I am thinking about doing the mod but am not willing to pay $200 ~ $250 for a glorified piece of plastic. I also tried Pedro's mod
http://www.pedrosgarage.com/Site_3/Make_a_Hi-Flo_Intake.html but wasn't happy with the result (actually more with my lack of skills in fitting plumping parts into my car).
So here's what I am planning to do this week:
I will re-use most of the original pipe and will get rid of the Helmholtz resonator. For that I will cut the pipe in two right in the middle between the rippled part and the resonator and will replace the shorter end with a 45 degree 3" silicon elbow pipe. This then turns this into a $20 mod
If you're interested I can let you know how it worked out