ibiza_cupra_gti said:
anyone tryed one on there car? let us know cheers

The Advertising Standards Agency banned them from making any performance or economy claims about their product, since they couldn't produce any evidence that they worked.

So, officially, they don't work.

Simon.
 
I had one too, was on a golf gti, kind of sounded like this, brrrrrrrrrrr...waaaaaaaaaaaaaaaaaaaaaaa, and it made no performance gains, £60 down the drain [:@]