The threads that the pistons go into that open and close the rear hatch were threaded and finally teh pistons fell right of them. Got those repaired for $57 and the hatch is functioning properly again. Only time I smell my exhaust is sometimes when the window is open, but it's not as bad.
I'm not really familiar with 5th gen tailgates, but look for any rubber bump-stops associated with the glass. Those bump stops can generally be adjusted in or out by turning them (the base of the stop is threaded). If the glass is difficult to close, thread them in half a turn and try again.
An easy way to find a small exhaust leak is to jack the car up, start it up and plug the exhaust with a rag. I've done it many times when working in a shop, and you'd think the car would stall, but they never stalled, just ran at little lower rpm, and you'd immediately see and hear if there was an exhaust leak, no matter how tiny!!!