New 05 Boxster S owner here. My manual says there should be a storage compartment in the space on the firewall between the headrests, but I have what looks like a vent or intake. I tried doing a search, but couldn't find anything.

 

it looks like you have the Bose optional stereo. That area becomes the subwoffer outlet. Put your ear next to it with you radio on. should hear something. Hope that helps?

 

Thanks! Been going crazy trying to figure it out on my own.