Will you gain HP and TQ, yes of course, but how much?? Hard to quatify. Tuning to the new parts makes all the difference! I can tell you this, after moving from a stock maf to a LT1 and translator, and eventuallly to an LS1 and translator, I picked up 2 tenths, and a 3 mph in the quarter, once I had everything tuned in.
BTW, if your reman'd maf isn't reading 255 at WOT, you've found one of the several issues with the reman'd mafs. You're leaving power on the table.