I also have a 2005 Subaru STi as well, with 1000cc injectors and a much bigger turbo (400hp to the wheels), it actually gets better mpg than my 2013. Its my street/race car, I dont hit boost till 4000rpm so I actually get around 26/27mpg normal driving and around 30mpg highway on long trips.
Ive driven from Cincinnati to Murfreesboro TN and arrived with a 1/4 tank left. In this STi, full tank to 1/4 tank is exactly 10 gallons and the trip itself is 330 miles.
1STi by
SplatSTi, on Flickr
620362_10151634281173032_878172471_o by
SplatSTi, on Flickr
10258645725_a9574d7d66_b by
SplatSTi, on Flickr