P0430
need help plzzz. I have a repeating p0430 code. I got some cats put on after having test pipes for a while to be within California law and I’ve ever since had a reoccurring p0430 that would go away for a bit after clearing it but comes back sooner or later. The cats are low miles I got from a friend. I notice when I drive the car around 2k rpm just cruising it will pop on the light. Before I throw money at it for a new cat,how likely can it just be a bad o2 sensor? I got them installed by a good shop so I’m not too sure where to start. I need to pass smog in a couple months.