P0420 cat converter bank 1 below threshold

[Peekirby-S3]

I’m getting this recurring code which sometimes disappears for days after clearing the code. When the codes there the car stinks of fuel and misfires when pulling off. When clearing the code everything runs perfect again. 
 

I’ve logged the voltages of 02 sensor 1 and 2 and there’s barely any difference between the two.

is this definitely a dead cat ? Is there any other tests I can do? Cheers