P0420 code help

I have a 99 Tacoma 2.7l 4x4 and I keep getting the p0420 catalyst efficiency below threshold bank 1.
I have replaced
-both oxygen sensors
-coolant temp sensor
-all exhaust gaskets
I have had this problem for over a year now. It only comes on when I go on a long drive 30 miles plus. Could this be egr valve or bad converter? I don't think the converter is clogged any help would be appreciated

 

converter. Fixed my 420

 

I'm going thru the same thing. I still can't find it either.

 

I had an exhaust leak at the flange when I got that code. Cut the bolts off, replace the gasket, new bolts

 

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