Help Codes P0420 And P0430

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This is from 98 Chevy C1500 With A New 5.7

 

Today the CEL came on. Codes came back as P0420 and P0430 which from I read indicates a problem with either the Cats, O2 Sensors, Vacuum Leak, Exhuast Leak or Fuel Leakage in the intake.

 

I checked my vacuum at idle and 2000 RPM it was in the green at a steady 17” so I do not suspect a vacuum leak.

 

I cannot hear or feel any Exhaust Leaks.

 

I hooked up my code reader while engine was running and both the Catalyst and the O2’s read that they were ready, so do I rule these out?

 

This thing sat for 3 months. Do I need to get it out on the highway and “blow it out”?

 

I put a new supposed 190° thermostat but the gauge reads about 170° and read 190° before new engine and radiator. Could the ECM be reading the low temp and dumping too much gas in the motor?

 

Could it ba a problem with the new Delhi injectors?