[MMGT1]

7X sensor at the back of the block and the connector from the IGM to that sensor. This has come up many,many times that I have seen. The connector and sensor are exposed to massive amounts of heat, the two wire lead breaks down and skews the signal to the IGM. Then the sensor it self has a plastic housing! Over time the housing heats and contracts so much the plastic breaks down and causes tiny cracks in the housing. This, in turn, causes the cracks to open up when hot and will also skew the signal to the IGM causing exactly what you have happening.
I would be looking to the MAF to be sure that it is not the issue. You said the MAF good, but get a scanner on it and move the wires as much as you can and make sure it doesn't screw up when you do. Also check the IAT sensor the same way.If you can find no fault with the MAF or IAT then go to that 7X crank sensor at the back of the engine.
**Reading what is happening to you it is a carbon copy of what I went through and it was a combo if the MAF wiring AND the 7X sensor that fixed mine man. Mine needed both to finally fix it