its very possible. i have a friend with an 04.5 with chip programmer intake exhaust and he averages 30 highway.
which is like 26 -27 using usgallons.
i havent got mine yet (3 more days boo ya) but i expect 20+
poor niave me.
i average 15 city 17-18 highway.
my friend with the 04 told me his was the same before the chip
i need a chip. :s
haha and tires...