I'm probably wrong but it sounds to me as if the stock MAF is FUBAR.
I haven't seen this mentioned yet but have you tried tapping on the MAF when the car is idling to see if doing so makes it stumble? Sure sign of a bad MAF.
It seems to me you've thrown a bunch of money at the car but haven't fixed/upgraded one of the most vulnerable systems it counts upon to run right.
Then again, I have a couple of the best tuners out there making my car perform the way it does. See my signature,,,,,,,,,,,,,,,,