Rotten egg smell is an indication of fuel getting to the catalytic converter, so it's possible that you are really running excessively rich.

I suspect a fuel injector leak, usual cause is varnish buildup making the valve stick. The proper way to fix that is to take the injectors off and run cleaner through them with a cleaning machine (edit: you can also force the valve to actuate using a 9 volt battery and clean the injector using carb cleaner). The home gamer way is to put a bottle of injector cleaner fuel system additive into the fuel tank and go highway driving for a couple of hours.

Failing that, the fuel vapor control system solenoid valve in the engine bay can sometimes fail and send fuel into the intake. You might try blocking off the hose between it and the engine; the valve sits on a bracket under the throttle body.

The O2 sensors might need replacement if they're old and slow enough, although from what I recall the usual failure mode for those is to read lean, not rich. I'd check the injectors first.

When replacing fuel monitoring sensors, be very sure that all your sensors are OEM or acceptable replacements from the OpenGK sensor list: Sensor Information - OpenGK
Using a single off-brand sensor will result in the car running wrong.

 

This is awesome information! Thank you so much I will try the home gamer idea here in the next day or two and check the fuel vapor control system. At least try to locate it and take a look.
Thank you again!