What I did instead of weld the flange onto the cat was I had an exhaust shop bend a piece of 2.5" so that it was the same angle as the cat. I removed the 1st cat entirely. No CEL at all. Don't know what emissions are like in your state but if you can pull it off go for it. 2nd cat I replaced with a high flow from magnaflow
. That tripped the CEL though. If you ever do that do not get a magnaflow cat. They are not obdII compliant as they say and they will not honor their warranty.
Ceramic coating is great. My s10 was just stainless (no coating) and the engine would get crazy hot, and it was only a 4cyl. I don't think trd headers are coated. I found a used set when I was looking to buy but I wouldn't get them bc they weren't coated. Also I lost the shine on mine (as they said I would) just something to think about. Any questions give me a holler