I have had my xfire for about 2 1/2 weeks now and i too have noted poor gas milage. I am down around 20 as well. My driving is no different than when i had my acura rsx type s which lists highway at 31. I would get close to 37 and now i am not getting barely 20.

I too use my heat seaters constantly and have heat on as well. maybe the missing piece of this puzzle is the seat heater?

i am hoping a chip and K&N's will help me get close to the 28 mark