this annoyed the out of me when i got my truck, i'll tell you exactly what it is...
its the crappy foam seal at the top of the hvac box that's missing air is rushing in outside of the hvac box.
my fix was to remove the outside cowl and then remove the seam sealer on the top cover plate and reseal with silicone the whole opening where the foam used to be.
if you want to be 100% sure, remove your glove box and go for a drive you'll feel tons of air coming through
its the crappy foam seal at the top of the hvac box that's missing air is rushing in outside of the hvac box.
my fix was to remove the outside cowl and then remove the seam sealer on the top cover plate and reseal with silicone the whole opening where the foam used to be.
if you want to be 100% sure, remove your glove box and go for a drive you'll feel tons of air coming through
