Greyson, I own a XFE model as well. I am averaging between city/highway of 35.1, i dont have a lead foot and dont baby it at times. Does your cobalt have any issues far as fuel odor smells after you turn off your vehicle? There's a recall for that if you didnt know.
You may need to visit your local dealership and see if they offer BG services. Ask for a fuel induction service to clean out your throttle body area and run some better fuel injector cleaner.
2009 Cobalt LS XFE U74
Mods: K&N Typhoon Intake, Option Cat-Back Exhaust, Cosmo Short shifter, Maxxim Ahead 17X7's, MPx shorty antenna, FE5 Strut/shocks, Tein S Techs, Moog endlinks, Moog spring seaters, ZZP shorty header, LSJ downpipe, LNF front grille