I had or still have the exact same problem. When my truck sat in heavy rain I would get a little puddle on the pasenger side floor. nothing I did could find the problem. I narrowed it down to possibly leaking through the door rubber on the top. It wouldn't do it sitting up hill only flat or down hill. you might want ot check out the rubber liner along the top of your doors or go buy a big tarp. I now have a parking garage so I'm not sure if the problem went away or not.