I had a 2000 Cabrio and had a similar problem. I was convinced it was the rag top leaking… makes sence right? NO! after weeks of investigation I finally discovered that the drains along the bottom of the frame were plugged with grease. Only the holes on the driver side were clogged, thus the puddles only on the drivers side. I cleaned them out and voila - nor more puddles. What was happening was since the frame is hollow and the drains plugged the frame would fill with water. Where there were screws holding the electrical in place the water would seep out and slowly leak into the passenger compartment.
And sincere thanks for the tip.