ScrappyDooDoo

Hi,
Deciding on whether to purchase a supposedly " Subaru Impreza WRX STi - Spec D " - with Pro Drive from a dealer. The Pro Drive is a cert as I've seen receipts - but not sure if its just a wrx made to look like an STi with pro drive.
I am a little mythed if it is actually what has been described - Was always under the impression Spec D STi should have satellite GPS, leather interior, and what alarmed me was when looking under the bonnet - I thought the STi was stamped into the Air filter? I didnt see this although all the STi badges were in the correct places. What should I look out for in a Spec D to tell it is actually a genuine STi - even what should I look our with a genuine STi. How can I tell it is what they say it is?
This leads me on to my next questions: I have the VIN number but cant make head nor tail of what it is - I know it was made in Japan, by Honda. The Car is a 2007/07 plate.
Any help/advice much appreciate. As you can see i'm still a newbie