Whenever I see moldy drywall, I recommend physical removal. But, every now and then I come across a project where physical removal is not physically or economically possible. The most recent case was a large (22000 SF) home under construction. The drywall was installed over metal framing prior to the roofing system being complete... and the rains came. This particular home is unique in that there is literally hundereds of miles of electrical wires, T1 lines, cable, phone, plumbing, conduit, ductwork, etc, and all of it goes through the drywall in the ceiling cavity.