Brian-Mc,
It could be a number of things. One is the MAF as you have stated in your original post, another could be the Fuel Table - Air Meters Backflow correction (as it is load based if I remember correctly). The backflow correction table will make a difference depending on where in the intake tract you have the maf meter installed. Also wether it is a draw thru or blow thru application. What load the engine is at when all this happens etc. etc. I had a problem with this in blow-thru when testing some things on my car, as the TB was snaping shut and causing a lot of backwash or intake reversion (even with blow off valve) thru the maf meter......
Another area to look at would possibly be the Accel Pump Table as discussed in the other thread....
Run a datalog to see what load is when this happens as turbo setups will have a higher load at lower engine rpm/part throttle conditions as you well know.
On mine I changed the backflow correction table from about .3-.4 load/1500rpm to 1.98 which seemed to help in my case. Still in the testing phases.....
Yours may differ depending on boost, intake tract, maf location etc.