Symptoms of faulty fuel injectors and/or a failed O2 sensor might include some of the following; Hard Starting, Poor fuel economy, Rough Idle, Car runs fine when cold and terrible when warm, Car will start just fine when cold and not when warm, Getting a fuel smell inside the car, Loss of power in acceleration, or Fuel leaking from injector seals or injector. Failure of either of these components almost always causes a "Check Engine" light on the dash as well.

If your having any of these issues I would first get the car scanned for any error codes (AutoZone will scan the car for free).

If the injectors or O2 sensor is bad they are just as easy to replace as spark plugs. My '00 RS has over 81k on it with out any fuel injection problems...it's gone through 3 O2 sensors, but every time the O2 sensor went out the Check Engine light lit up like a Christmas tree!

Editted to correct my horrible grammar!