can anyone confirm my exhaust problems

[unmeloy]

I have a 2009 4.2 le finder with about 80,000 miles. since the day that I got it about 6 months ago I have noticed a faint sulfur smell from the exhaust but the vehicle is not throwing any codes. now I am smelling a strong ammonia smell and still not throwing any codes no other issues with the vehicle whatsoever and I have stock exhaust. I only get gas from two stations and run that gas in both of my vehicles and only having this problem with the Pathfinder. anyone give me any insight on this please.