could be the injector. Get a fuel pressure regulator, and hook it up to the fuel rail. Turn the key to the 2nd click, just before crank, and listen for the fuel pump to cut on and off, have a buddy read the fuel pressure. It should initially read I believe (correct me people) 30 to 40psi, and more importantly it should remain with that relatively same amount of pressure for about 15-20 mins without dropping very much. If your pressure gets up to 35ish, and drops rapidly, the pressure is getting bled somewhere. Then you start narrowing it down. I wouldnt jump right to an injector as the cause thoug, it could be a bad regulator, or fuel pump, or even a vacuum leak. You just have to narrow it down. Does the car run fine, and accellerate of when its running? does it stumble at idle? Keep us informed.