I recently bought a used E46 that has the "stink" problem. I had the evaporator treated twice, and this improved the situation, but the car has given myself and two others asthma even after the treatment. I agree that a permanent fix is needed, not just a workaround. How did you wire the damper in the duct to stay open? Has anyone found out any further info about how to permanently fix the problem? Does your evaporator look normal when you have the "stink" problem? Would there be any obvious signs of mold? I took the car to an independent BMW shop and they found that the evaporator looked clean.
Thanks for your help.