Just had my single turbo setup tuned by rdz and maxed my stock maf out at 380whp at 9.8 psi. They claimed with an uprev maf I should be good for 440-450 wheel. This was a mustang dyno btw

 

I ran my stock MAF along with a MAP set up for a long while. The MAF would peg out at 5 volts when the MAP was near 6 psi. You have a few options to monkey around with the stock MAF - increase the size of the tube the MAF is placed into, narrow the hole exposing the thermisistor, or add a fixed resistor in series to keep the voltage below 5 volts as the air flow increases.

I always wondered why someone didn't just tap the MAF wiring but insert a MAP sensor, temp sensor and retune... I think it would actually cost less and work better than a new high flow MAF.