Welcome to Ecomodder. This is the most helpful group of people I've never met. There is plenty you can do to boost your FE. I'd say start with figuring out how to drive like a hypermiler first as it will take time to learn, but will also give you the greatest improvement over any mod you could do. If you want to do some mods, I would start with anything related to improving aerodynamics, because that's a big factor in your highway mileage.
Start here:
100+ Hypermiling / ecodriving tips & tactics for better mpg
You can find mods here:
65+ Vehicle modifications for better fuel economy