For a two stroke to run "clean" it's mostly a matter of just running well, properly tuned and maintained w/o an excessive oil/fuel mix.
I've often said that a motor mildly built for performance (ie not NOS or hi-comp mods) will be more
reliable not less and get greater efficiency as well. I can't help but think that work-arounds such as catalytic converters on two strokes were conceived by those with more an interest in appeasing the ignorant than any actual, functional first hand engine experience.
A poorly running engine pollutes far
more than any performance motor contingent on only one variable - the operators restraint, not flying around at WOT all
the time lol
Along those lines, 'Top Gear' did a very interesting (if admittedly biased) study of a BMW M3 against the much touted Prius, thought ya'll may find it interesting: YouTube - Prius More Environmentally Damaging Than BMW M3