Having trouble with my truck. Blowing whiteish/blueish smoke.?

i own a 99 dodge ram 2500 v10. i was helping my girlfriend move when all of a sudden i was at a stop, put it in reverse and heard a bang behind me. Looked back and there was a black puff of smoke. turned it off, tried to turn it back on and it wouldn't start. after letting it sit it started. drove it home and took a look at it. the engine was running rough so i figured maybe it was an electrical problem. i changed the spark plugs and the number 1 and number 3 plugs were shot. i replaced them and the #3 plug still wasn't igniting. changed the wires, wasn't the problem. looked at the coil and and its throwing a spark but the cylinder still wasnt firing. I changed the fuel injector on that cylinder and it didnt change anything. the catalytic converters were also both blown out. I don't know what else to replace. It's currently blowing white and possibly blue smoke out of one exhaust pipes, the side the number 3 is on (true dual exhaust) . I may try the oxygen sensor next but i don't know what else to try. if anyone could give me a direction to go in I'd be extremely grateful.