I hate to be "That guy", but this has been covered over and over again.
The usual questions turn up:
Are you accounting for the different gears and tires?
Manual or automatic?
4WD or 2WD?
Mostly City, or Hwy use?
What weight oil are you using? Engine? Axles?
What kind of Fuel are you using?
What pressures are you running you tires at?
How do you drive:
Are you aggressive, or do you relax and let traffic do it's thing? How do you come off lights?
I think the 4:11's are too deep for 32's, but that's a gut feeling. For the best Hwy miles, since you have an engine that has bottom end torque, you want to take advantage of that. Did you change your Speedo gear, or calculate a factor for your tires/gears?
Auto's generally get a tad less gas mileage than a Manual.
Extensive City use tends to drag down the MPG figures.
Heavy, high viscosity oils have more drag than low viscosity oils. 5-30W for regular oil, or even lower if Synthetic are EPA "gas saving" oils.
Running low pressures on the street is a sure fire way of getting low mileage.
Lastly, how you drive will have a large affect on your mileage. Jack-Rabbit starts, stop and go traffic, and driving aggressively will waste fuel.
Relax, don't be in a hurry, use a lower gear in "creeping" traffic to crawl along at idle just enough to plod along behind the guy infront of you.
Accelerate smoothly from a stop, and decelerate smoothly from Speed.