In his book, Marching Toward Hell: America and Islam after Iraq, Michael Scheuer provides a tantalizing glimpse into a collection of documents that he provided to the 9-11 Commission that details the American response to the threat posed by Al-Qaeda. Naturally, I immediately had them FOIAed for and eagerly awaited the CIA's response.
I was informed that the CIA's response was very negative. You can see for yourself that the CIA not only invoked the operational exemption to FOIA requests given to it by the CIA Information Act of 1984, they would not even confirm that the files existed. Nor did they give leave to appeal their decision. Overall, a total FOIA block.
P.S. I included the pages from Marching Toward Hell in which Scheuer describes the files on the off-chance that someone else wants to submit a FOIA request.
CIA Shoot Down Scheuer FOIA