To which I would add:

Nin-firing injectors are often just lightly stuck shut with gummed fuel. Before pitching the $100 injector for a new one try freeing it first. Pull off the entire fuel rail with all wires and hoses attached. Turn the key to the 'on' position a few times to build up pressure (you should hear the pump run briefly each time). Leave the key on. Then under the hood observe the injectors as you push the throttle open. They should fire in pairs back and forth as the throttle opens (the high tech 'accellerator pump' function). Look for any that aren't spritzing. There is a small metal pin on the end of each injector - if you press it in gently with a small pointy object (like a finishing nail) it will break the stick and most often resume a fuitful life. Run some FI system cleaner through the gas to prevent them from resticking the next time it sits for a few weeks.