Here are some dyno's of minimally modded cars:
http://www.ft86club.com/forums/showthread.php?t=47001
http://www.ft86club.com/forums/showthread.php?t=47868
I don't feel much of a difference, but I'm still pretty happy with it. I currently only have a drop-in filter and a TRD exhaust.
The great thing about the OFT is that there are OTS maps already built for my future mods (E85, headers, superchargers, etc.)