I noticed about a 2mpg increase with what I have, but then I mounted some E load tires and it went down by 3-4 mpg. Thing is I knew that would happen so now I'm sitting around 16.1 mpg avg.
I do not have an after market exhaust, but I had my K&N before the lift and tires. Stock I was getting 22-23 mpg hwy. After lift and tires I am getting 17-20 mpg on the hwy. Depending on how I drive.