Ok i had a CEL when i had a test pipe on. I since replaced it with a high flow cat. Right after i had the HIgH flow cat i reset the ECU. THe cel had gone away. I was driving today and the CEL came back on. I checked all connections etc... I was at the dealer for a oil change cause it was free. Did something happen since then?or is this the random misfire thing. I guess ill have to pull the code.

 

a buddy of mine had that happen and he runs a hi-flow, he bought that O2 extension and it turned off after like a week or something like that.