If fuel economy raise... probably the catalysator/DPF FILTER hevily glogged.... it will raise fuel consuption and exhaust back pressure... IT will not open with driving pedal to the metal!! have to drive over 80km/h 30min stable pedal or cruise control (DDE/digital diesel electronics will then automatically activate the DPF REGENERATION/cleaning function ... (sorry for my english) and some of ecu remaps will fuck up this function... that's why i would newer remap my car(diesel)... powerbox (p-tronic) is much better
