For molten filament to jam at the inlet to the thermal barrier tube like shown here, there must be something wrong with the cooling in your setup. The cold zone needs to be cool for the extruder to work right. It looks like the cold zone is not staying below the glass point of the plastic, so the filament softens and mashes into a jam.
Here are some common ...
"Im guessing its the mightyboard or the power pack."
Right track there.
Usually this symptom suggests your heaters are overtaxing your power supplies.
Since you swapped extruders already, the heating elements and sensors in those are not likely to be an issue. That leaves the bed heating element and power supply.
A resistance measurement can help rule out ...
Most Stepper drivers will have lots of energy passing through them so it is crucial to having a moderately sized heatsink to cool them off otherwise they will get too hot. Most stepper drivers found online come with heatsinks but you could search online for mini heatsinks.