Unfortunantly, there is a big difference between what the EPA fuel economy estimates are and what you will see on the road - that is all that the sticker is, just an estimate.
But there are some things you can check that will definitely get the MPG numbers to go in the right direction. Just need to get a little more info.
- Is this the 5-speed, 2.7L variant (just guessing from the mileage description, that is the only one that can hit that kind of mileage)?
- What are the driving conditions - is a mixed city and highway driving or more city or more highway?
- What are the conditions of the plugs, plug wires, distributor cap and rotor? Have they been changed out?
- Cleaned the throttle body? Replace PCV valve?
- Check tire air pressure / alignment. Might need to plump the tires up with some more air = less rolling resistance.
- Could also be a lazy O2 sensor, as they have a finite lifespan. Usually good anywhere from 60K miles to little over 100K miles - might be time for a new one, especially if the mileage has been consistently getting worse and maintenance is always up to date.