The main purpose of “de-smogging” a FJ60 2F is primarily clutter abatement. There’s so much crap in the engine bay that’s associated with the emissions system.
I wouldn’t get hung up on the phrase “de-smogged”. Think of it more as junk removal. If it doesn’t bother you, just leave it. If you lose sleep over it thinking about it at night- tear it all out (carefully).
Some of the quasi smog components are actually good to have (Hot air intake, Hot idle compensation, PCV) so getting rid of all of it just for the sake of de-smogging isn’t ideal.
The catalytic converter does drag the engine down but it also does good too - air pollution is horrible