Ammonia/Cat Piss Smell

[bmrboi2]

I have this smell coming from my exhaust. I have scoured around and found some of the most ludicrous reasoning from idiots who don't read the actual issue. This is coming from my exhaust at Idle after a cold startup and its only on rare occasion. It doesn't appear to be environmental just totally random.

It's not inside the cabin, it's not coming from the vents, it's not under acceleration that I can notice (Followed my husband one day) I am just hoping that it's nothing wrong.

There isnt anything wrong with the cooling system or the ac system....aside from thrust arms needing replacement and new rear brakes....not a friggin thing wrong with this vehicle. Any Ideas?

The one thing that I saw seemed intriguing is to change gas brands. I have been using Costco gas regularly in all of my vehicles for years and never had an issue like this. The 5er and the old X5 (Same 3.0l 6) never had a smell like this, ever. I'm stumped.