I have my second appointment with the DMV tomorrow who wants to see the emissions sticker before they will register my 2008 Boxster (purchased out of state). I pulled up the carpeting on the bulkhead behind the seats expecting to find it there, but nada.
When I lived in Phoenix, I had to take my car to an emissions station where they hooked up a code reader to the boxster. They look for any failing codes that deal with emissions. If your car passes the emission test, then they would give you an emissions pass letter, which I would then take to the MVD and then I could get my registration. Not sure if this is what they are talking about.
Turns out it's located on top of the engine cover. You have to disconnect the convertible top to expose the top plate covering the engine. Definitely a PITA, but not something you need to do on a regular basis.