When I purchased this Bonneville in January the inside of the back up lamp lens were discolored by rust. The previous owner had drilled holes in the bottom of the lenses I asume to drain them. I went to my local GM dealer and ordered a new lens assembly(the complete lens that mounts to the deck lid) and the wiring harness which includes the sockets because they were also rusted. Installed and had no problems for about a month, here in New England it was too cold to rain. The first rain storm we had the b/u lamps filled with about 1/2 inch of water. Took lens back to dealer and exchanged for a new one. Good for about a month, I sealed the the complete seam around the lamp with silicone and it still leaks, sealed the sockets with electrical tape, still leaks. Dealer exchanged for another new lens, first washing, leaked. Any thoughts????
Does any one know what SSEi stands for?

Doc, have you looked at the trunk lid to see if any holes are there where the light assembly is attached to that may cause a leak?
And to answer your question, SSEi doesn't stand for anything officially, but there are those that have taken up the task of making it stand for something anyways. My personal favorite is "She Stomps Everything?! interesting....."