On my '99 Silverado 1500, there almost seems to be a fresh air vent down by the floorboard on the passenger side. During the winter months you can hardly stand it -- feet & legs get ice cold, etc. I have eliminated the possibility of a door leak as it is coming from further forward in the cab. Has anybody else had this problem/know of a fix for this problem? (besides shoving a sleeping bag/jacket to plug the airflow...)
Thanks!

I have the exact same problem with my 2000 Silverado and have yet to hear a solution. I called dealer and they said bring it in but might cost hundreds of dollars to find air leak! So being from south carolina the winters are not that cold so I have just been ignoring it but still would like to fix it,