It's not your issue though. I've run a one wire O2 sensor in the 7747 ECM with long tube headers and it still runs fine. Just not in Closed Loop much.
There's also a change needed in bin when you move the O2 sensor that far. But again not your issue, would still run well.
the painless harness does in fact have connections for the egr valve. gry/red pnk/blk wires go to the egr solenoid. this is for painless harness part numbers 60101 and 60201
Could it be possible the Prom, Chip, got knocked slightly lose in the rollover?
Just a thought.
Will check waiting on a scan tool I ordered to give some real info