Tore it out to find the leak and well that was easy to spot. BTW, nice work MB for having bottom cushion and the seatback share a connector so you just can't set the bottom aside.
Problem is, a fix for this? I cannot locate any rear seat inflation parts diagrams for even a potential replacement.
Slideshow: A one-of-one U.S.-spec Mercedes-Benz SLR McLaren Roadster became even rarer after a factory-backed transformation at McLaren's headquarters.