(not the happy ending I'm looking for but this)
After 6+ years of owning this car I found the noise that has been there from day 1.
Dealer had it the third day I owned it and could not duplicate problem, lol.
I've had people lay in the back and try to pinpoint where the noise is and all say like I thought, some where by the rear fender well.
I find the problem by accident when I was working on the car, I tripped on some tools and caught myself against the door....... and I heard that very distinctive sound !
I FINALLY FOUND IT !


I was going to video more after it was apart, lol, but I got too excited (I mean its been six years) when I got it apart and fixed it.
The problem was the bolt plate that the door latch striker bolts to was not spot welded and there for loose and made the popping sound.
The fix was to take small pieces of sound deadner and put between body and bolt plate for the striker, tighten to specs and WOOOOOOOOOOOOOOO HOOOOOOOOOOOOOOOOOOO !
The sound is gone !

 

Always nice to fix an annoyance such as that! I have one in my front end for the life of me I cannot find

 

Right on, noise gone.