i think a couple people have tried it on their own (or talked about trying it, at least)
and a few have even made external hangy-wormlight things..
but no actual afterburner-esque solution has been paraded around here, as far as I could tell you.. and I don't think you'll see one any time soon. your best bet is to try and sell your current model and put that $$ towards an official FLU unit, I'd say.
or keep waiting for the "do it yourself" kit that was announced the better part of a year ago, and looks like it's vapor pretty much... sorry man...