[Mike C]

My buddies Chevelle sounded like it had glasspacks on it as well. We have the same mufflers, and my Camaro sounds great. The difference? A balance pipe. I'd zip back to the muffler shop and have them fix you up if you don't have one.

Another thing to consider is the new exhaust change your jetting requirements. Backfiring in the exhaust is a sign of an over-rich situation.

Other than that, don't know what it could be.