Like dmsfun says, do the throttle body cleaning and add a catch can, almost before anything else. Since you just recently bought it, I would highly recommend you do a complete major service and inspection of the entire vehicle, paying particular attention to the drivetrain. It doesn't have to all be done at the same time but, this involves changing all oils/fluids/filters (some you've already done I see), install good quality copper core, properly gapped spark plugs, make sure the air filter is clean, etc. etc.
While your FE is not too far off, you may have other issues too. Some of the sensors, especially if you have high miles and have contaminated the system with cleaners, may not be functioning quite as they should. The main ones to be concerned with are the IAT Sensor, MAP Sensor, and O2 Sensors. You can replace all of them for under $200, with the O2's being the most difficult to replace. If you have an exhaust leak, your FE will also suffer, as the O2's (if working properly) will sense a lean condition, and dump more fuel into the engine. With my mods. (in the summer non ethanol fuel), I usually get ~13-14 mpg in town, and ~20-24 mpg (normally ~22 mpg) on the highway....driving 65 mph in 4th gear, MDS on 90+% of the time. Also, remember, these slugs weigh in at almost 4800 lbs. without you and your stuff in the vehicle. Tough to do a whole lot better without some serious mods, especially in town. All of my mods, for the most part have been relatively non-invasive.....most I've had to do is remove the valve covers, rocker arms and front cover.
Edit: I just noticed you have an 05, so you should also check the ignition wire resistance to see if it is excessive.
Strongjeff, you cheat though....having headers on that cool running V-6. And, didn't you say your were 2WD also...~500 lbs. lighter?
