Keep in mind, a manifold leak will most likely make a slight ticking sound. Also, check to make sure there are no leaks near the Y-pipe and the EGR. We own an expedition that was doing the same thing. My wife drives it. She smelled exhaust just as you described, but she never told me she heard a slight ticking sound in the AM, It was a cracked manifold.
Let me know what you find.
Friday, April 8th, 2011 AT 2:19 AM