I custom made an H-pipe with 2 big Magnaflow cats. That's the only emission control device I run on the car when I go through emissions; No EGR, no smog pump. I don't put anything in the tank, and I make no adjustments to the fuel pressure or timing, nor do I pull the spout. It aces emissions every time. Last time it went through I did 10/182 on the HC, and 0% on the CO. It has more to do with your tune than anything.
I have collector car insurance, and I am not exempt. I think it has to do more with the age of the car than anything else. Here in GA, you are exempt when the car gets to be 25 years old. I can mail you my cat pipe in 2020.
Kurt