I am looking to get the best milage possible from my GT sedan. Currently I get between 26 & 28 mpg. What are my options to increase that to say in the 30's?

Keep your car in a "good" tune. Keep your tire pressures at the max recommended by the tire manufacturer. Easy on the a clean airfilter, fuel filter. Keep your windows up. When on the highway use your cruise control. Those are applicable to all cars. If you can keep your foot off the then some of the smaller mods will help as well. Those being CAI/FWI, Ubend delete, freerer flowing mufflers. By using my CAI my highway miles went from 29 mpg to 32 mpg (calculations based on miles traveled compared to gallons to fill my tank and for all those DIC dis-believers mine was only off by .2 mpg)

Like just said, keep vehicle tuned up with OEM only stuff. Run good quality tires, and keep the pressures up. Keep oil changed as well, preferably synthetic if you wanna spend the $$. Oh, and drive like your about 85 yrs old!