I have an fg xr6 na with about 14000k's and getting about 600-700 to a tank depending on how I drive but will never get less than 600, try taking the restrictor out of the air box and putting in a KNN filter and re setting the computer by taking the battery off for about 10 mins and let it re tune your car to having the restrictor out, I found it made a massive difference about 450k's before the restrictor and KNN filter to getting 600-700 now