I have a 2023 RKS and when purchased I had Rinehart 4" mufflers installed and after a few weeks took the bike back to dealer and had a CR480 cam installed - only mechanical changes made so far. The performance has definitely increased with the cam install but thinking of adding the Rinehart headers - anyone have any guesstimates on the additional performance increase adding RH headers? 

Hey bukkers, mate there maybe some folk on here that could give you a solid answer like Lushy or Hoody or fella's with that tuning/building business background but unless they pop in and see this it'll probably be crickets, have you asked on Harley Tech Talk? It's an American forum, shit loads more members than us, you are welcome here though, you will get an instant reply there, be careful who you listen to, some will spend your money to confirm their own bias.

I cannot give you an exact answer, but if you lose the cat and get a better flowing header, you will get a wider spread of power, maybe 3-5hp more and a cooler package, as far as engine heat goes. You will also get a bunch of noise, you may like that. Not sure. Where are you HP and Tq wise now??   

Also as Cats are ZDDP sensitive you can run a better oil .  

I’m looking to de-cat my RoadKing 2011. I have S&S mufflers. It’s plenty loud enough now. Will removing the catalytic converter make it a lot louder?

HOG63 . Yes