1997 Chev S-10 Obd II code P0420

Hi, I had my 1997 Chevrolet 5 speed S-10 truck (138,000 miles) tuned 4 months ago. I kept getting P0135 code. I tuned it myself, wires, cap, rotor, plugs etc. Also installed 4 new O2 sensors. Yesterday I got the
idiot light again. This time the code is P042. I checked manual and it says " Catalyst System Efficiency Below Threshold". Any suggestions on fixing this one would be appreciated. My wild guess is catalytic converter is bad??
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Stop guessing and have it analyzed with an OBDII tester. There are many conditions that can cause the converter to look bad. Also if you were running it a long time with misfires the converter could have been destroyed. Check all the connectors on the O2 sensors. Check for other codes...

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If P0420 is the only active code, then most likely the converter is bad. If the car was misfiring for a long time the converter may have been damaged.
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Robert Hancock Saskatoon, SK, Canada
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