I have been doing a bit of digging on the same topic. The 8th digit of the VIN is a 7 - that means turbo SFI 6-cylinder. I think you also want to look at the RPO sticker in the trunk - you should have LC2 for the turbo 6-cylinder engine.
Someone mentioned there being a VIN imprinted on the frame? Could someone verify this and explain where it is located? I guess if it is imprinted on top of the frame (between the floor pan and frame) it would be hard to see without lifting the vehicle.