I've added the possibility for users to search through their sent and received PM:s to this hack. Instead of selecting a forum to search for, an PM-option can be selected instead. There is also a quick search box added to the PM box on My Home.
At the moment the code is a bit ugly, it works, but since the search is somewhat different for PM:s there is a lot of if statements. I don't really like that everything inside the loop that iterates through the search results is within an if statement and it does different things based on if the user searches the PM:s or the posts. I've also done an extra template for the PM:s search results. But I've used the normal search script because I didn't want to have two search pages and much of the code that builds the query is the same.
If anyone is interested in this hack I'll try to clean it up a bit and make instructions for it.