Chevrolet Repair: Sudden loss of power, chevy s10, muffler shop

Question
It came on suddenly. When I left home, I heard a hissing noise that sounded like it was coming from behind the cab of my 2003 Chevy S10 2.2 liter truck. It has 49,000 miles and in the past two months, I have replaced the fuel filter, fuel pump, plugs, and wires. The sound it makes when pressing the gas reminds me of a compression release. With the vehicle running and my wife revving the motor, I traced the origin of the hissing sound. It appears to be between the catalytic converter and the muffler. Underneath, it sounds more like a sucking sound. I couldn't find any vacuum hoses loose or anything disconnected anywhere. I drove to Auto Zone and had them test the codes. It showed missing on #4 (fixed now)and low catalyst. I hope I gave you enough information, and thank you in advance for your help.

Answer
Hello Kerry,
Sounds like a plugged exhaust system. Could be the muffler, or the converter.
I have seen screens inside the tail pipe get covered with rust flakes, and restrict the exhaust.

But if you had a bad miss on a cylinder, and ran it long with the miss, the raw fuel can cause the converter to melt down inside.

You might want to temporarily disconnect in front of the converter, and go for a little ride to see if it runs better.
Or go to Midas, or some other muffler shop that can test for restrictions.

Van