My case is as follows, as the standard car my Pajero constantly returned 8.5 lts per 100 kms, after fitting a front bar, heavy bash plates,roof bars , 65 lt auxillary tank and heavier tyres the car always returned 9.5 to 10lts per 100kms and constantly needed to unlock the torque converter on the slightest grade . After the Horse Power Factory worked on the ECU it now returns less than 8 lts per 100kms and is far more lively than before , now I know you rarely get something for nothing and if you fully use the extra power fuel usage will suffer but so far the car is quieter, more responsive ( when required ) and more economical even when towing . As far as I am concerned there is no downside except in the minds of others !!