P0420 come back

Thread resurrection.
I want to follow up with the same symptom in my 2007.
This might be another thread resurrection I can follow up my 2007.
I have a 2007 Prius
The "Check Engine just lit up 2 nights ago as I was pulling in the driveway.
I put the scan tool today and its says "1 fault" and it displays this:
P0420 01
P0420 02
I was also a victim of a stolen catalytic converter and replaced mine with aftermarket 2 years ago. I bought the replacement aftermarket probably 120 dollars and have it installed professionally. Basically no leaks.
At first time replaced, it was running nicely with above 45 mpg on the screen. After a year it went down to 41-43 mpg.
My car is fully tuned up and serviced as what the book requires on maintenance service.
Presently it has 151k miles and eats a 1/2 a pint every 4500-5000 miles of driving. I use 87 regular gasoline.
What I did yesterday is I, I cleaned the throttle body and intake, run it half an hour, change oil and filter 10w/30 Quaker State synthetic (as I always use every 5,000 miles, air filter is clean and not due yet so I installed it back. I reset the check engine light using the scan tool and maintenance after the change oil. After 100 miles of city and highway driving, the Check Engine turn on again. I also want to add that besides the check engine light, the car still runs beautiful. Here is my last screen right when I was heading home. Any suggestions? Thanks.
If I need to change the 02 sensor and it could be a part of it, I wont mind changing them. with the original Toyota parts. The only thing that I cant afford to put back is the original catalytic. its too expensive.