GM Started in late August/September adding the 4G onstar before the refresh. The only way to know if it is an i series is on the sticker, the will be an Interim Processing Code.
If it is a Denali, it will have the 8 speed transmission.
Are you a GM representative or a representative of the owners of this site or are you just someone on a mission from God? No offense but there is no way I am sending any info to a stranger.
I know I can duplicate this effect on all of my suburban type vehicles I have owned by cracking a rear window by itself. I understand this is happening with all the windows closed on the new body style, but wonder if the fresh air intake is causing the pressure to rise and fall in the cabin creating this butteting noise?