I agree, the wiring tray that passes down the drivers side and also behind the driver seat..the carpet comes up by prying the door threshold strips up ..These splices in your excellent photos dont look oriignal mercedes to me..never see anything like this in mysystem.

I had a little mouse nest in the foam box of my vacuum pump case and they nibbled the wiring but caused no short circuits..But like you I found the wiring tray soaking wet and the cloth wrapping was rotted. 95 e320. Good to remove the stinky mush and dry out the tray..