It appears that the Search function does not return any threads/posts prior to 2008.
This is both in the Advanced Search and the search within a member's own threads/posts (at least mine anyway).
I've done several different searches for different things and this seems to be a consistent problem.
As an example, do a search on E85. The results I get return nothing prior to 2009.
I you get a result which show a thread started by Nix in 2006, then perhaps there is something wrong my ability to search.