hI ,MY QUESTION IS I HAVE A COLUMBIA WITH C 13 ,MY MPG IS 6 UP,I THINKING TO CHANGE MY TRUCK IN THE FUTURE I LIKE 1 WITH LESS MILAGE RIGHT NOW I HAVE 770K, I SEE PLENTY COLUMBIAS WITH LOW MILAGE WITH C 15 ENGINE,ONLY I THINK THE MPG FROM C 15 IS WORSTER THEN MY C 13,CAN I FIXED THE C 15 WITH ECM TUNING OR STAGE 1 TUNING TO HAVE A GOOD MPG TU 6 UP,THANKS FOR YOU ANSWERS