exhaust popping noise on deceleration?

[kjoyes]

I am getting a popping sound on deceleration around 2000rpm.
any ideas?
i removed the main cat, the oxygen sensor plug was lose. i welded the plug on. repaired some holes in the flange as well.
cat is still off so i can really notice the popping now. So i think my problem is before the main cat
before i remove the cat i got obd2 code of P0136
O2S-12 (Bank 1 Sensor 2) Circuit Malfunction
I bought 6 coil packs at the local savage yard and replaced my front passinger side coil pack.
(because the coil was grounding/shorting out. making clicking noise.
that didnt solve it.

[1986nate]

that would be a backfire...