Not to bring this post back form the dead, but...

The blower unit in the Z looks exactly like the one that was in my Supercharged Frontier that had an in cabin air filter except.... Backwards! I haven't had the guts to actually remove the blower housing to see, but it sure has had my curiosity up ever since I installed my new sound system. Not even sure if it is worth it, if you have to drop the blower to change the filter. Meh...

 

Then what is the white filter that I can see through the vent on the right side of the steering column? If you look through that vent on the right side of the drivers dash, you will see a white air filter on the upper left area of the air vent. At least on my '06 it has one.

 

I always thought the Z had one... I'm a smoker and I smoke in my Z frequently. But everytime I jump in the car, I never smell any smoke or cigarette traces. Same goes for my non-smoker friends who sit in the passenger seats.