3 years is far far too long to run a single set of copper spark plugs and they are too cold for your mods.
It won't make a huge difference but maybe some, but swap those plugs for some AL 605's and only run them for around 15,000 miles. The waste spark ignition system we have tends to make the plugs live a short life. At only like 12 bucks for 6 new plugs its super cheap anyway.
Another thing that will affect it mpgs is your speed. Which I figured you'd already know, do 65-70 instead of 75 on the freeway and you'll gain a mpg or 2 easy.
