I have this problem as well, and I did a little research on it the other day. I found that there is an AC system component that is plastic that goes into the cab through the firewall under the cowl area. I think that is where the water is getting in. However, since it is under the cowl itself it is impossible to get to. I could feel the leak because when you close the door with all windows closed up you can feel a puff of air come out in that area. I am pretty sure this is the problem, but pretty UNsure of how to fix it.
