a little wager.....backfiring

My truck went off like a shotgun out the tailpipes when I flooded it and killed the battery. When I did get a fresh battery, the fuel vapor in the exh fired in both pipes... BANG!!! the neighbors at my apt came out and asked who was shot....lol. The timing was fine, it was all fuel. So, without knowing more, I'm going to say 50% likely it's late timing or firing order, and 50% excess fuel. By each other a round...lol