Hello, New to the forum with a 2004 A6 Quatro. I searched the forum and read about the plugged drains under the battery tray, and sunroof drains, thanks great info. We had some heavy rain last week and the car sat outside and left me to find a soaked passenger floor. I pulled the carpet, the trans controller was dry, but a lot of standing H20 around the plastic box. I cleaned up the H2O, dried the foam and carpet. I pulled the battery and tray to find the rubber drain under the tray was missing, so it wasn't plugged! The other drain under the brake cyl. was plugged solid and there was a derbies in the well. Cleaned all that out.

Update...
I cleaned the drain under the brake cyl. and put things back together. With the carpet pulled back, poured water into the battery tray, I used a funnel in the battery drain hole to eliminate any other possible leak source and it is almost instantaneous. The water is coming in just below the evaporator drain valve. There are 2 raised "nipples" in the pressed metal on the firewall, the water runs in from the left one just below the evaporator drain valve. I can't get a good look yet, could it be the seal around the evaporator drain valve where it passes through the firewall? Can I remove it from inside the car and re-seal it?
Need some advice, Any other suggestions??
Thanks