Moose,
The Vin number will only denote if the vehicle was a turbo car. 7th digit is a 7 if it is a tubo car I beleive. Look at gnttype.org to verify that. What you really need to look at is the RPO code sticker in the trunk of the car. Make sure the RPO code sticker has the same vin number as the vehicle. Look for the WE2 rpo code. You will know for sure then that it is a true GN. Hope this helps.