What color is the porcelain on the plug? If it is black or "near" black is when you'd be too rich. If tan, brown or light grey I'd think they were OK.
Back to the cat... THERE lies the smell. You need a larger cat, or at least another cat. The 350 chevy trucks in the 90/91 era came from the factory with too small of a cat and they had a potty smell... The fix was a longer cat, and it worked. Do you have the ENTIRE FACTORY exhaust? If the cat was advised by a local muffler shop, I'd go to them with the thing hot and smelly! Get em to give good converter.
Big Jim