i say start small since youre not going to track it. Diff brace 1st sway bars and links 2nd. See how you like it and if still not to your liking go on to coilovers/suspension arms. But i think the first 2 for the street will make a good difference.
make sure no intake leak. looks like that can be pushed more in? reset and see if code returns. maybe o2 sensor harness damaged during cat install? or can just be from going catless.