Vortex exhaust

[oddball]

Hi,
Just curious if anyone else has a vortex  fitted on FD, and if so, did they find any of the claims of better performance combined with better M.P.G. to be correct.
I had one fitted some time ago.  Am I the only one?  I was led to believe that they have fitted these to lots of rotaries, and if that is true someone on here must have one.
Comments please.