I'm getting exhaust in the cabin, so lets start with the basics. This is Thea, a 1980 Avanti II. It has a nearly new stainless steel exhaust installed by Jon Myer before I bought the car from him. I can't hear any leaks, but my ears suck. The trunk seal looks OK, not pristine, but not badly cracked and no serious cracks or lost chunks. It seems to close correctly and fully. The exhaust tips extend past the lower valence as they should. If the windows are all closed and the vents open, no problem. I'm not sure about if the vents are closed. Windows down, all is OK, but some smell enters the cabin with either with any of the other glasses open or shut. If the windows are up and either the vent wings or rear vents glasses are open, I get exhaust inside.
Where do I start looking for this?