For 2 years or so I have been enduring this exhaust smell in my car. I tried to adjust the trunk latch so it would seal better. I was at the most extreme setting and still I was seeing light get into the trunk. It was not a small gap. So I decided for a cheap temporary fix just to see exactly what the problem is. I got a $3 roll or rubber weatherstripping and applied to to the trunk lid. Closed the trunk and drove. It’s been about a week and ZERO exhaust smell In the car! I can’t believe that I let this go in for so long and never fixed the issue! Well here is a pic of the stuff I used.