So there is no secondary O2 sensor on our bikes. That’s why it doesn’t throw a CEL. Which also means, it is not running anymore rich, since it doesn’t use a wideband O2 to adjust the a/f mix.
You are smelling fuel and noxious fumes that are normally neutralized by the metals in the catalytic converter. You will smell it at stop lights and especially at idle when the bike is warming up.
There should be some dynos out there for the RC390 or Duke for before and after removing the cat.
Record a sound clip? I’d like to hear it. Though I knew when I got the bike it will never sound “great.” It’s too small of a single cylinder to really ever sound super cool.