180* tstat will lose mpg without any performance increase.
Blocking off EGR probably will, too (without any performance increase) if you ever do highway driving.
Headers will gain like 2mpg.
Tune will get back some mpg as well.

At your mileage, your spark plugs are toast. Stick in some new stock iridiums or Autolite XPs. May as well replace your plug wires while you're at it. And take out the stock airbox and slap a huge cone filter on. That'll increase mpg as well.