I dont experience this popping noise all of the time,but say when I'm driving through a parking lot at low speeds and i get into 2nd gear,when I let off of the throttle I'll hear a pop sound from the rear of the car. I was thinking maybe a bad u-joint,but I may be wrong. Any help is appreciated.My trans am is a 1996 and an A4 btw.

 

Looking at your cars specs, I do know that a really free flowing exhaust can cause pops or flames.
(No Cats too).

I have a buddy with a 99 Mustang and his does it all the time when downshifting.
And I've seen a Subaru that lives in my neighborhood with No Cats on pop when he lets off throttle.

I hope that helps

Is it a light popping?

 

I'm pretty sure it's not an exhaust pop,but thanks for the reply! I'm really leaning towards a bad u joint because I also experience vibration at high speeds..Think I'm gonna get under it today and do the driveshaft test lol.