When I was a young man in the 80s, there was these Neodymium Super inductors (or magnets) which you which you fastened around your fuel line to (so the claim said) improve fuel consump'. I bought one and fixed it to my Mk1 Fiesta which I always had recorded the MPG (something I still do to this day with my current cars). I couldn't tell any difference in the MPG with the magnets attached, but hey, I think the things only cost £19 then. A small price to pay for the knowledge of such devices.
Chris
Please note