Ok please do not flame me or anything, but i got worried, a few months ago i put some megan HFC's on my car. As expected, the cel came on throwing P0420 and P0430, then, after almost 8 months, i turned on my car yesterday and the light wasnt on. It worked cuz it turns on when i put the switch in the ON position, but it's not on anymore. Did the code cleared, did the problem solved by itself (doubt it ) did the car adjusted the A/F ratio???
I'm more worried now than when it was on. Is this normal ECU behavior or what? Please someone chime in...

 

Sometimes they come and go. Check it with a code reader the underlying code is probably still in there.

You need a tune like we talked about