Howdy! And welcome!
So, I have this sort of symptom on my same year Hemi as well. I've asked around and there are two possibilites for you. First, you have an exhaust leak somewhere on he exhaust tubing itself. Second, and mor elikely, your exhaust manifold bolts (one or more, on one of the manifolds, aka headers) have broken, and you're experiencing a leak at the manifold directly off of the motor. I belive this is my issue, but I haven't dove much into it due to lack of funds, and life in general. The only way to rid this issue is to replace the bolts, but if the manifold(s) are warped, you'd have to replace those as well. Good news is you can install either "shorty" headers, or long tube headers in the stock manifolds place, which will give you a bit more performance, and probably a bit better sound. Shorty headers from what I read, will mostly bolt into the stock ones place. Long tubes however require more of a customization of your exhaust system, due to being longer than the stock manifolds. In turn, this will give you a bit more performance over the shorty style.
Hopefully I hit most of the points, if not, someone else will fill in, or correct me haha!
