Just a heads up to all you owners of the new body style 07 and 08 Sierras and Silverados ...I just noticed my truck had a smell of mildew inside and I found that I had wet rugs in the front and a bit in the rear. I checked all the TSBs and found none decribing what I found. Behind the rear seats there are two plastic vents( one on the drivers side and one on the passenger side behind the rear seats) that snap into the body sheetmetal and they were leaking water into the truck and causing the smell and eventually would have rotted my truck. My fix was to pop out the plastic vents( they are easy to pop out) and run a bead of silicone around the rubber seal that had already worn out with only 8000 miles. Then crawl under the truck reach up between the cab and the bed and snap the vent back into place I had to unbolt the rea seats to access the vents. You can check to see if water is starting to trickle in if you remove the seats and using a hose run water between the cab and bed and look inside for leaks I was shocked to see lots of water getting in the seal of the vents. My rugs were more wet in the front than the rear because the truck sits lower in the front and the water would run down under the plastic step sill trim and pool under the front mats and be wicked up by the padding under the rug and it would stay wet and start to mildew. If I did not smell the mildew I would have never known I had a leak in a basically new truck.