Your MAF should be fine. If it was the issue, you're engine itself wouldn't be albe to even idle properly.
O2 sensors would usually throw a check engine light on.
So it sounds like one of two things -- you may be running to high of a continuous boost which causes the ECU to throw into limp mode. Do you have a MBC on the car? If so, dial it down to 12-15psi and run it hard to see what happens. I know it's chipped so it should be able to hold the boost without being thrown into limp mode, but hey, you never know
Or the other option is you have a vac leak somewhere in the system, but not big enough to affect lower boost ranges - only the higher boost ranges. (more boost = more pressure on the tear thus causing it to loose all of the boost)
That's what I can think of on the top of my head.