Here in Lithuania we often have rain, I've noticed that trunk of my 05 ap2 is often wet. A friend from JoVa-Tec gaskets advised to check the light seals, after removing the rear headlight here is what we see, a leaking gasket is the main problem (shown with arrows)





here in eastern Europe it's hard to get the oem seals, they produced a set of high quality neoprene for me. I've tested it, and looks like the leakage is gone, yay!

 

FYI you are not a vendor.