Years ago I read a report where a catalytic converter was removed from the bike leaving everything else as it was. There was a before and after dyno test. Surprisingly, the results were that removing the cat has just a negligible increase in hp. There is no large increase. It was as if removing it isn't worth the effort.
Even in magazine reviews back in the day, when the factories started adding them in the exhaust, the review would state that the addition of the cat had no effect on rwhp.