Catalytic Converter Diagnostics

[tobyw]

Anyone know if there is a feasible way to determine if you have a failing (partially plugged) catalytic converter WITHOUT pulling it from the system? I have read a few conflicting statements about the ability to test it with an infrared heat gun, looking for a temperature delta at the inlet vs. outlet, but nothing concrete...

[Lurch]

You can remove the upstream o2 sensor and put a fitting in and attach a pressure guage.