I bought a nice 98 1500 4x4 5.9 last week. Drove it home about 270 miles and got a Catalyst Inefficient code on the way home. I used an infrared thermometer on it and prior to CAT was 300 degrees. CAT was 200 and exhaust right after cat was 200. From what I have read here this is not good and the CAT should be hotter that exhaust going in if it is working properly. Am I correct that the CAT is probably bad? Looks like it was replaced as some point. I have not gotten the code since I cleared it after the trip home, but a few times now I have has a sucking sound from the throttle body while idling a snot runs a little rough bit clears up after a few revs.

 

May be a hollow cat..... Are there inspections or tests where you live?

 

No inspections in Florida. I just ordered a Magnaflow CAT 3 minutes ago.