Rotten Egg Smell from Tacoma?

I put TRD approved tru dual exhaust out the back with the TRD thrush mufflers, did not change the cats, and the smell went away. Maybe materials in stock exhaust or mufflers?

 

Exhaust.....I think this is a common Tacoma problem, actually I think its a common Toyota problem. Because I have smelled it behind other toyota's as well. Anyway, I think I have read that dealer blames it on sulfur in the fuel, and they won't switch out with new cats. I have never had a Toyota before this, and never had that odor. But, I only smell it once in awhile maybe if I'm backing up with windows open. Its weird to me that I have never noticed other brands doing this besides Toyota, not sure why that is. But, I kid my 6yo son saying he farted, so we get a kick out of it.

 

As someone already said, a common Toyota problem. Very prevalent on the 1.8 Corollas a few years ago.

 

Gear oil gives off a nasty smell too after heated. Could this be a factor? Rear end...