[wp-hackers] Filter hook that affects xml-rpc data as it goes out

[David]

I am trying to provide a method to edit a database field that my
plugin has added through my weblog editor. The way I would like to do
this is have my plugin prepend a text string to the content as it goes
out over xml-rpc, and strip it back out as it comes in. The latter is
easy with content_save_pre, however format_to_edit doesn't seem to
affect xml-rpc data. Does anyone know of a filter that does?