Use Article Samurai.
Most of the time it will produce human readable content.
You can even load the txt files, bulk conversion mode...
You dont need to feed any synonyms, it does everything automatically.
Site is http://imxsoft.com/articlesamurai
P.s I am the owner/creator of article samurai.
Dont take my word, read the reviews on the site.
Regards
Do the articles produced by Article Samurai contain spun code?
Or you could try the one I wrote, similar to PAR.
http://www.articlerewriter.co.cc
Download the full version and PM me for a serial #.