Okay so I have had my 3" Catted DP and 3" Catback for awhile now but I was having some issues w/ the Dynomax Super Flow muffler I had on there so I had to take it off and I replaced it with this:
Megan Racing Turbo N1 Muffler

The exhaust as you see comes w/ a Silencer that you can put into the tip of the muffler that decreases the sound level by atleast 30%, it drops the tip down to basically a 1.5"-2" whole which would basically give me some/alot of my backpressure back. Now I have ran without it for about 2-3 days and I put it in yesterday for the whole day. Mostly b/c I love being able to hear the loudness of the S/C, being that I cant hear it that good w/ it out. So today I decided to take it out so that the car would sound mean again and now I have throw a P0420 code(Catalyst System Low Efficency) twice today. People say this is a common code when your Cat is going/gone bad. I havent done any hard pull yet to see if I am throwing some major knock or not but from what I can tell it has been fine. Now here is my question, could taking that silencer out and putting it back it have tricked to the computer into throwing this code b/c of the backpressure that the car was used to for a day and now it has less? Or is my cat really going bad?

If you could answer any of my question for me that would be great b/c I am ready to get to the bottom of this. Sorry for the long post but I was trying to explain what my problem was, Thanks in advance guys!

 

it could cause it, i had that code and i just turned it off usually happens with a new exhaust or change. unhook ur battery for like 20 min and rehook it and see if it relearns it. usually that helps.

nothing to worry about though

also could u get a sound pic of it in i hate my loud corsa and i want something quiet

 

Will that make my tune go away?? I dont think it will but I was just asking. But mine is loud without the resonator and it basically sounds like a stock exhaust exhaust w/ alittle rumble lol

 

hmm interesting. and no turning off a code wont mess up your tune

oh wait u mean having the computer relearn.... good question haha

i dont think it will considering if ur battery dies you dont have to go back to the dealer everytime to gett it reflashed. but im not 100% sure

 

Well, your car porbably got used to the flow with the silencer (since it restricts the flow), then without it the 2nd o2 sensor was tripped due to the change. I'd say just reset your the code and see if it doesn't come back without the silencer. Backpressure doesn't help your car performance wise, only sound wise, i don't find the point unless you have problems with cops.