Been lookingat improved MPG through remapping and just watched a fifth gear episode where they tried to improve consumption because of rising fuel prices. They used a VW on a circular test track with a measured gallon offuel and recorded the distance.To reduce fuel they removed excess weight like the spare wheel and jack, fitted it with low drag economical running tyres and gave it a remap MPG based, for a cost of £350. A repeat identical run was done on the test track and they where about 2 miles shorter than the first gallon so not even as good MPG. The out come was the remap was even detrimental to the economy, the technical bods did say they would expect a better result on bigger diesel engines but even so if you where to get a slightly better result how long would it take to get you're £350 backbefore you see a profit. [also if the remap gives more power and torque I would probably use it and push the juice through even faster].