I found this in the AudiWorld tech articles. It's the cat-diode mod. I just installed it tonight and will report on its effectiveness. This may be a solution for cat DTCs with hi-flow cats and aftermarket downpipes. I have the Wayne Angle Block already installed but still can't get the readiness code set for the cat.

Anybody done this?

 

nope, angle block fixed my CEL after 42DD downpipe install.