i have a kkm, cai, magnaflows, no resonators but not the xcal and it seems like i lost mpg but this is a direct correlation w/ my driving habits. when i got these mods i tended to hit the gas more. but on times that i just cruise to work and back it does seem like my mpg is a little better. i remember when i had just put my cai in, my mpg had gone up to 17.8 from my regular (where it's at now) 16.8.