I've done this with my zetec turbo mk4 fiesta. I've got a speed corrector kit.....will find you the link. The correction factor is too far out......With no corrector the mtx75 and mk5 clock combo will read 150 mph at 50 mph road speed. The software in the corrector allows it to go down to show 75 when doing 50. I bought and made a microchip programmer and re loaded a modified hex file onto the microchip and it's now perfect.if you buy and build the kit.....test it, and then send me the chip ill reprogramme it for you and send it back

Matt