Your shadow should be pulling 28 - 32mpg EASILY..
its slightly lighter than your turbo coupe and they both have a turbo setup, but the shadow has the sohc 8v 2.5 while the turbo coupe has the 2.3, so it should even out..
If i'm able to pull low 30's in a 2.4 dohc 16valve truck while hauling a couple hundred pounds of headstones and cement, you should easily be able to smoke that..
Work on that shadow more..