Exhausts 300 -Removing cat

If you removed your Rebel 300 muffler, you no longer have a cat (it’s in the stock muffler). One of the things a catalytic converter does is change hydrogen sulfide from the gasoline into sulfur dioxide, which has no odor. If the converter is removed, there may be a smell like rotten eggs or sulfur. Unburnt fuel due to no catalytic converter produces the odor.