One of the biggest design flaws in the M3 has to be how when you open the trunk on a rainy day, water from the deck lid rolls on to the rear glass and into the trunk. Well I think (hope) I've just installed a simple fix.
Found a carbon fibre spoiler for the rear window that should defect the water to the sides and not into the trunk.
Found a carbon fibre spoiler for the rear window that should defect the water to the sides and not into the trunk.