LynxCub

Hello All, I'm actually the guy with all the issues listed. My brother was helping me out. Today I replaced the Cat. Pipe and replaced both front and rear O2. The cat pipe is a Federal vs California. Reset the engine errors codes, and will drive it. Hopefully I won't see another check engine code. Can't Remember the error code, but per AutoZone, the readings indicated: 1) A/F 2) Cat. If this fails, how do I go about checking the ECU for open/close? Thanks for all your help!! :-\