I researched different threads and didn't find any answers, so i figured i'd post my issue and see what anyone has to say. A couple weeks ago I installed my y pipe, all the o2 sensors plugged in, and the car runs and sounds great except for the fact that my check engine light came on a few days after intall. The code on the OBDII reads p0420 which is inefficient catalytic (bank 1) and I cleared the code then it came back. My assumption is the cat-less y pipe put a lot of stress on my main cat (187k+ years old) and it is pretty much done. Again that's an assumption. I do feel a decrease in power, and now I can smell the exhaust inside the car at times.

My question is which of the following should I do at this point in order to maximize my maximas performance again AND clear check engine light:

1. Purchase a new cat, install it
2. purchase a high flow cat and install that.

Again I don't know whether the high flow cat will cause another code or not that 's why I'm starting this thread, to get opinions. Another point is if I purchase a new cat will that one get destroyed also from the y pipe or was mine just old? Only helpful responses are appreciated and thanks in advance.

 

I have an aftermarket cat a Walker brand, it wasn't that expensive. I did not receive any codes after I did a y pipe. Did you use new crush gaskets where it attaches to the manifold, or did you try reuse the old ones because you should just replace them.

 

I made sure to use new gaskets, I was going to install it myself but I had my body work guy (who is savy with exhaust work" put the y pipe in for me installing the new gaskets with it. I think i'm just gonna buy a relatively cheap new cat like what you have and it should be sufficient. Thanks for your response i'm still under the assumption that my cat is clogged and needs to be changed