I don't want to piss on anyone's bonfire but, spot the obvious flaw in this plan.
Unplugged the MAF......didn't feel any difference either way really. Just as bad tho 

I'd see if you can cancel the order and just do a bit more investigation.
Try resetting the codes (and disconnecting the battery for 30mins or so). This will reset the ECU trim values.
I'd put money of it being the lambda sensor over the MAF. Have you got the car mapped?