What causes this? It does not smell like eggs or oil, it is just a stong exhaust smell. I have no exhuast leaks and cannot smell it in the Jeep unless I have the top down or a window down and the wind blows the right way when I am stopped. My Jeep passed emissions two years ago but I think the smell has gotten worse. My exhaust is loud which I guess is not normal for a Jeep, and it does burble on down shifts and engine braking (coming down from 2,000-2,500rpm) and I ocasionally get a pop/puff sound from the back of the Jeep during the shift after a long uphill drive at a little above 2,500rpm. My Jeep is not lacking power (insert 4 banger joke here) and I got 16.5mpg last tank so I think it is running fine. I am just curious as to why it has a strong exhaust smell.