Odor from doors?

I have a 2004 Nissan Titan. I thought the odor was coming from the AC so I bought a can of spray from the auto parts store that is supposed to clean the ductwork for AC and vent which are separate in this model. I changed the cabin filter, the drain is clear, but when I roll down the windows while in the vent mode, I get a foul mildew odor that seems to be coming from the doors. The drains in the doors are large and clean, so there is no stagnant water laying in the bottom . Any ideas?? This only happens in the vent mode!