Has anyone went from the double throttle body intake manifold and converted to a single throttle body intake manifold that is seen in the Armada/Titan/QX80? Would it be a hard conversion to do? I understand tuning and tweaking the computer would be needed to make it work with only one.

Don't believe I've seen this attempted in this community.

I think you'd need more than tweaks to the firmware, there's at least a whole code section you'd need to bypass. There may or may not be a version of the Titan/Armada/QX80 firmware with all the same sensors and controls as the M, but that would be the best solution if it exists. One thing that might work is rewiring to feed the single TP, MAF, and IAT signals into both corresponding inputs on the M ECM, then dummying the current from the missing TB with a load resistor. That way the ECM should think it's working two TB's when it's really only working one.