speedhawk deisel engine tuning

Has any body fitted a deisel tuning kits to their freelander TD4? this model supposedly plugs straight into the ECU and takes over, increasing BHP and Torque, with the side effect being upto 20 percent increase in economy as well! can anyone tell me do they work? i would love to confirm.
Steve.

you will get more power , but it will be thirstier, or if you drive moderately you will then get more mpg, you don't get both together.