In my 535is, I had all the same problems you are now facing. My leak turned out to be the windshield. I know it is a tough nugget to swallow, but a new windshield, gasket, trim strip and professional installation did the trick. Luckily, I took a rock hit on my old windshield and so insurance picked up a bit. It fixed the problem. Unfortunately, my 535is was rear ended and totaled after that. So I decided to yank the interior and everything else. Getting the carpet out was the hardest part of my dismantling of the car. I had everything out of the car, dashboard--soup to nuts. I recall still getting stuck around the a/c condenser fittings and heater unit --both of which I had removed. I ended up cutting the carpet and chucking it, only after much knuckle busting. What I would do now, and will do someday on my M5 is to go the leatherique route for the restoration of the leather. They have a website. I also used resolve carpet cleaner on my rugs with great results. I am thinking about using leatheriques carpet fixer upper, when I get to the point of dealing with the faded rear "hat shelf"