Bad catalytic converter?

Does anyone know how fast a catalytic converter may go out? And could I test the problem by just removing it or opening up the exhaust in front of the converter to see if it is the problem? Or does the motor need a certain amount of back pressure to run? Also is there a sensor on the throttle body that controls fuel pressure and is it very exspensive to replace?
thanks for any response
Tucker

easiest way to check cat is get a vacuum gauge and hook it to manifold vacuum, warm engine up to operating temp them rev engine to about 1000 rpm and watch gauge, if cat is bad vacuum reading will start dropping. the fuel pressure regulater is on top of throttle body, easier to just get another throttle body if yours is bad. pressure is supposed to be 12-20psi while engine is running