Originally Posted by G-Benz

Rotten egg smell is emitted from the sulphur byproducts used in your catalyst.

It may still be fine, unless you are experiencing performance issues...in which case, it might be clogged.

Battery sulphur vapors don't smell like rotten eggs...smells like acid, and your eyes and nasal passages burn! First hand testimony to this when my voltage reg. gave out and over charged the battery, causing it to boil and vent!