I got a CEL today with TC1-P04020

The error code was Catalyst System Efficiency below threshold (Bank 1)...

I assume one of my 100cel cats (fabspeed Supersport) has finally gone bad???

Any other ideas?

 

If you do some highway driving the heat may burn off some carbon and improve the cats. Don't drive so fast that the ECU goes out of closed loop.

 

that's pretty much all I do...highway driving...

The CEL came on when driving locally (slow driving).... we'll see... worst case...i'll go to a straight pipe only system...

 

Or you can go with an exhaust with 300 cell cats to avoid this problem....

Like ours.

 

That is exactly what code I got running the FVD straight pipes, driving on the highway no problem but I get stuck in a traffic jam and the CEL goes on.
That is when I decided to install my Fabspeed Sport back on to avoid any CEL's until I get the chip tuning for the straght pipes. It is possible that one of your 100 cell cats have gone bad.

BBGT2

 

that exactly my problem as well.. 100 cel cats 0420 code.