yo; before you open it up; how about removing it?
aww. I can't see your year info in reply mode!
On my 96 I have basically 2 cats; a reduction & oxidation -
Use PB Bl;aster; etc. liberally on all fittings for O2 sensor, air tube, and clamps (the muffler clamp came off ezily on my 96 2 weeks ago! after 14 years and 2 months on it!
Here is a pic showing some of the fittings by Steve83
http://www.supermotors.net/registry/media/71635
some more vac gauge test info;
"...The easiest test for converter plugging is done with a vacuum gauge. Connect the gauge to a source of intake vacuum on the intake manifold, carburetor or throttle body. Note the reading at idle, then raise and hold engine speed at 2,500. The needle will drop when you first open the throttle, but should then rise and stabilize. If the vacuum reading starts to drop, pressure may be backing up in the exhaust system....If there appears to be an exhaust restriction, disconnect the exhaust pipe
(MIESK5 NOTE; or Muffler) just aft of the converter to relieve pressure and recheck the readings. CAUTION: The pipes will be hot so wait awhile for things to cool down. If vacuum goes up and/or backpressure drops, the problem isn't not a plugged converter but a plugged muffler or collapsed pipe. If there's little or no change in readings, the converter is plugged..."
Test, General
Source: by autos.yahoo.com
http://autos.yahoo.com/maintain/repairqa/battery_electrical/ques083_0.html
and;Vacuum Test, General (Click Inspections); Vacuum Test, General (Click Inspections);
"...You may also take the converter off the vehicle and check it for damage or clogging. Shining a flashlight into the core of a honeycomb style converter will reveal whether the honeycomb is partially clogged, damaged, or loose from the edges...."
by walkerexhaust.com