[Megahurtz]

To shed some light here, his ECU is pulling a ton of fuel by the short term trims, yet the Wideband is still reading way rich(.70-.78 lambda) at cruise and idle.

The O2's are switching but not very much because they are just seeing an overly rich condition all of the time. Yet the injectors MS time in the log is lower than you would expect for the lambda the Wideband is reporting. The narrowband O2's are showing equally rich on both banks and will be pulling 25% fuel out yet the wideband is still rich.

So my summary is that either all of the O2's are fried from using the exhaust as the ground for the MIG welder. Or that unburnt fuel is making its way into the exhaust on both banks by misfires or dead coils/plugs on both banks. Nothing else really makes sense here.