No physical damage will occur to the stock 2gnt MAP sensor from running it under boost.

You just need to limit the voltage that the stock pcm sees from it.
I limit the voltage to 4.6V with a simple circuit I built consisting of a resistor and a zenor diode. It's simple, it's reliable, and it works perfectly.

As far as the fuel injectors go...
The stock 2gnt fuel injection system is a sequential injetcion system, hat is it fires each injector at the time it'e needed... however if you know anything about sequential fuel injection, then you'll know that it can only work in sequential mode at idle and lower rpms, because there is only so much time available in which you can inject sequentially. Sonce a certain rpm/load point is reached on the stock pcm it has to revert to a batch injection system of sorts.

The whole batch vs sequential arguement is one that still rages, however on out engines, batch injection of the injectors works perfectly. If it didn't I wouldn't be able to idle on 780cc injectors now would I.. ;)

As far as the setup that I use ont he Megasquirt, I run the injectors in Alternating 2 Squirt mode, basically this means that for every 720 Degrees of rotation of the crank, you get 2 squirts, first on injectors 1+3 together, then 360 degrees of crank rotation later you get 2+4 squirting.

Hit me up with any more questions that you have.

Oh yeah, get rid of the returnless fuel setup, and run a return line from the valve on the end of the fuel rail.

It is a lot harder to run and tune a turo car without a return line... I have seen this in person.
If you have no return line then as boost increase, the diferential pressure between the fuel injectors and the intake air pressure decfreases, thus the effective size of your injectors decreases as boost goes up.
Run a return line, it's simple, it works and it's safe. Not to mention easy to tune.

Lee.