Random pictures that you did not take.

[HO455]

I'm no expert but I will share what I know.

If your getting the rotten egg smell out the exhaust that in a good indicator of a cat that is no longer working properly. Most newer cars will give you a code if it isn't working correctly. Hence the upper and lower O2 sensors.

The best test to see if it is working is an emissions test.

You can test to see if it is plugged yourself. Just drill a 1/8 inch hole between the engine and the cat and hook a 0 to 20 PSI pressure guage up to the hole. If it reads above 3 PSI the exhaust is clogged. You will need to rev the engine up to be sure it is not clogged.

If you get a high reading then drill a 2nd hole after the cat and test again. If the cat is clogged you will get a lower PSI. If the PSI doesn't drop then the plugged area is farther down the exhaust pipe.

After testing you can plug the hole(s) with a self-tapping sheet metal screw, tap the hole for a machine screw, or do a plug weld. If you weld it shut make sure your ground lead is attached to a clean area near the hole your welding closed.