i dont know where too look first. foot through the floor or driving mrs. daisy MPG doesnt change. about 8.5-9 . any ideas would help. i dont know a ton about diesels yet, this being my first. so thats why i dont even know where to start looking. as far as mods go, bone stock, egdge evo, 4'' cat back no muffler. napa filter. its an auto with a 6'' lift 35's thanks alot!