Stand at the back of your vehicle while someone else revs your engine a bit,......if you get nothing but a whooshing sound........I would take it to a muffler shop for evaluation........there are generica catalytic converters available at muffler shops that might be OK for your particular state's/County's inspection procedure. If you are in an area where no exhaust emission test is done, and you suspect the cat,.....try a "test pipe".............that's a staight pipe replacement for the cat...........if it fixes the issue, then you will have to decide whether you can live with the test pipe or if you need to move forward with a new cat.

BC in Austin, TX