Infinite, not zero
00-01 had a small enclosure and 6x8s. Anything newer has 6x9s with no enclosure. The cutoff date iis fuzzy, so it may be a mid 01 change, mid 02 , or 01-02 change.
Regardless, gen 2s have no enclosure. I fit two 8" Kickers in the shelf with some trimming and bending and MDF adapters. They are "infinite baffle" Subs so they don't need an enclosure other than the trunk. The back window really limits the space with which you can physically work with (the space you can fit your hands and tools iin).