02 avalanche 2500 cold air blowing in by passenger feet
 

I brought the truck to my mechanic & my body shop and all the vents moldings and weather strippings were checked for defects. Also Smoked was forced into the car from a wind machine to see if there were any other exterior leaks and nothing was found. But when it is cold and we are on the highway the passenger has to cover his feet with a blanket because they actually freeze. Has anyone else had this problem? Any suggestions would be helpful.. I have had this truck from day "1" and it has never been in an accident so structural damage cant be the answer. Thanks in advance for any HELP!!!l