I found out that my water leak was coming around the gas cap area. There is a small drainage hole but, that wasn't the main problem. Plugged with a rubber stopper nonetheless. It was coming thru the metal seams around the gas cap area. Poured a cup of water in that area and sure enough. That was the problem. Put some silicone and resolved the problem. I also checked the drainage holes of the sunroof. There were four of them but, they were ok. Also, I put some silicone around the rubgber grommets of the wheel well. I think there were like 6-10 of them. Don't exactly remember. I also put some undercoating spray around the wheel wells because, I noticed over 13 years of having the car. Some of it came off and could see the bare metal. Do a water spray down test around the gas cap, sunroof(on the outside of the sunroof rails-4 total-each corner of sunroof), wheel well area, spare wheel area, and get the windows again. They might've installed wrong. Also, look around the trunk lid weatherstripping area. Try testing that area also. BTW, I have a '87 560 SEL for reference. Hope you find the leak soon. It's still Winter. One more thing, if there is noticable water coming in. It is most likely coming from the top or side of the car than, the bottom. It also depends where it is leaking in the trunk. Mine was leaking on the very edges of the wheel well inside of the trunk and leading to the bottom passenger-side corner. Hope you find the problem.