They are usually just a resistor in the line from the air temperature
sensor. All they do is enrich the mixture, so you use more fuel than
you need. They do not increase performance (apart from the oil
companies balance sheets, that is). Complete scams. Don't touch them.

--- In mazdamx3ownersuk@..., jappocketrocket
<no_reply@y...> wrote:
>
> of course. :-)
>
> has anyone fitted any of the gadgets on ebay that promise to boost
> power/
> economy/ performance etc?
> do they compromise reliability or anything else?
>