Does the spedometer show the correct speed or is that incorrect as well? Not sure how a 2004 mod works but if both the speed and k's travelled are out I would think the sender end of things ie. gearbox. If only the distance is wrong, I guess the cluster somehow "calculates" the distance from the speedometer, either mechanicaly or electronically. Small descrepancies somtimes occur because of wrong gear ratios, wrong diffs or different size wheels, but 5:1 is hugh.