Further, while driving around and keeping one eye on the scan gauge and switching through various modes noticed it's switching to open loop mode and that's when the issues start. It seems that open loop tries to keep the auto in 3rd so when it reaches the point you'd expect it to change up to 4th it stutters & surges.

Is this a by product of a MAF fault as well, a result of the lean situation or something else to consider?

Am going to search for a 4.6 MAF to swap (even if it's for a trial (is the 4.6HSE rangie the same?)) to see what happens. Anyone have a spare in Syd to trial for beer?