Ml320 misfiring after ice storm

[GlassMonkey]

The car was running fine when I parked it. (Way overdue for plugs and wires but running fine. Then there was a big ice storm that basically encased the Benz in about 1/2" of ice.

After thawing it out it barely started and needed constant throttle to run. I changed plugs. (they were in terrible shape) and it ran a little better but still misfired. Then I changed the coils and wires. Now it will idle on it's own but it's still misfiring on one (I think) cylinder. I've double checked wire connections/ order. Is there something I'm missing? I used all the correct (ridiculously expensive) parts.

No sign of head gasket damage, no smoke, starts in normal amount of time

Thanks for any help!