You have recived good info from the above posts-I'll add a few more items to check.
The first thing I would approach would be the thermostat on the air intake-It pulls hot air in when the cars cranked in the am. It can go out and pull hot air all the time and make the car run poorly. I took mine completely out and hooked a lager hose into the airbox and really picked up some power that you can feel in the seat of the pants.
Next thing is to inspect and probally replace all the little rubber elbows on your vacuum hoses. Any vac leaks will play hell with engine power and fuel economy. Along with the vac hoses is the vacuum tree that all the hoses go to. You will need to take the 10mm bolt out that holds it to the intake and replace the O ring that seals the part to the intake. I used permatex silicone safe form a gasket blue and just glued it back in-will be hell to ever take out again but I doubt I'll ever need to.
Another thing is to look between the intake and the engine block where they bolt together-if you have a red intake gasket by all means replace it with the newer green one thats out there now-couldn't belive how much better my car is running since replacing that sucker about a month ago.
Hope that helps
Poolman