Yeah I've come across these before, a piggy back device is normally a tried and tested chip which alters the signal to and from the ECU to improve performance, not a cheap assed resistor. My guess is that it tells the ECU that it's getting more air than normal and richens the fuel supply (and I bet the fuel saver chip does the opposite!) to *maybe* get you 1-2bhp, but I'd be very wary of such a thing, better off getting it superchipped. I did find the fact the dial is fitted on a Ferrari funny, I bet it's not wired up! not a bad profit... 5p resistor sold for £30 * guliable chavs from max power = Ferrari 355 plus enough left over to stick a fake dial next to the gearbox to help advertise! *takes deep breath and climbs down off soap-box* :angry: