I HAVE A 2003 TAHOE Z71 WITH LEATHER SEATS. MY WIFE NOTICED A SMELL AND THOUGHT IT WAS EXHAUST. I DROVE THE VEHICLE AND IT DID NOT SMELL THAT WAY ALL THE TIME. WE FINALLY FOUND THE PROBLEM BY MY WIFE GETTING BURNT. HER SEAT HEATER WAS GETTING WAY TOO HOT AND PRODUCED A BURNING SMELL. IT GOT SO HOT THAT IT LEFT A BURNT MARK ON THE LEATHER SEAT AND BURNT HER BACK AND THAT'S WHEN WE FIGURED OUT THAT IT WAS WHAT WAS CAUSING THE SMELL. BE CAREFUL WHEN YOU TURN ON THOSE FRONT SEAT HEATERS. WILL REPORT TO CHEVROLET. *TR