So, my cat's clogged up and was sending its code when I got dyagnostics done. I got a 3" downpipe from ZZP. Just wondering if the code will go away when I install it.

 

Hard to say since you did not share what code your got.

If it's a P0420 code and you are not using an OEM cat, you stand a chance of getting the code again. You mentioned a ZZP DP, if this has a high flow cat, you stand a HIGH chance of getting the code again, even though there may be nothing wrong. The O2 and PCM is calibrated to understand readings from the OEM cat, so non-OEM cats don't always play nice.

I offer a service to delete the P0420 code. See the link below:
https://montecarloforum.com/forum/pr...impalas-42773/