You might be getting a little worse MPG with that charcoal filter clogged and if you haven't checked the air filter, its probably got half of moab in it.
I only have the lift, but I'm hitting 17 if I split my mileage with city and two trips to Boulder in traffic per week. Pure city, prolly 13.5 (wife). Pure hwy, 19. I'm due for tires asap, so we'll see what one size bigger does to it. I've found driving habits will vary that quite a bit. I consistently get better miles than the wife, but she hammers the throttle and brakes and I tend to predict stops and coast a bit. On my trip home with it from Kali, I was at 20 something but I was on cruise and trying to see how high it would go. The later one's have a nav view with a "live" status bar. I've found that lugging up to speed produces worse results than just giving it some juice, not flooring, and then getting into coast mode as quickly as possible. But that's boring, and the V8 just wants to be exercised!