Anyone know what symptoms would be present if a catalytic converter was plugged? Just changed out an Idle Air Control Sensor & a O2 sensor. Previously it was running really rich & idleing speradicly. Since I've replaced the sensors its not running rich anymore & still idles a little odd. Not sure if I need to adjust the timing or the cat is plugged. The truck is running better but seems to hesitate or be slightly uderpowered, when excellerating occassionsally she'l run great with plenty of power. Just thought I'd ask you guys for some advice on trouble shooting. Thanks!!