When you said GSR and 4G93, they just get confused between the 4G63 they have and understand. To be safe, they'd rather said that MAF-t is not going to work with your setup. What will happen if you can't make it work with your car while they have said it will? They can't give any advise either because they don't understand 4G93T.

If you want to go for MS, opt for MS-I. either v2.2 or v3 is no different. Only the injector control hardware is different. No problem if you use a high impedance injector or low impedance with resistor pack. However v3 have a better injector protection circuit. The choice is yours. MS-II is not yet running at it's full steam and is not suitable for GSR-t which is running wasted spark. It's still under development in alpha stage but MS-I is ready for all cases and it's proven to work fine.

When ordering MS, you need extra IGBT component to run the extra coil channel. Other than that, you can choose either to use the std. map sensor or 4 bar map sensor with barometric correction. You also have to choose either you want to use the stock coolant temp sensor or their GM cts. You also need the open pod air temp sensor for turbo application plus the bung to be weld on to your intercooler piping.

summary of parts needed for GSR-Turbo.
1 MS-I kit with case.
1 pc VB21 igbt.
1 pc coolant temp sensor.
1 pc intake air temp sensor with bung.
1 pc 4 bar map sensor. (2.5 bar map sensor is included with the order you don't have to order the 4 bar map sensor if 1.5 bar pressure is more than enough to run your engine).

You also need some extra components that you can buy cheaply here in Jalan Pasar for some mods in the assembly. (Some tricks of the trade to make it work for your GSR-T) and also some extra enhancements such as shiftlight, tachometer, launch control, full throttle shift etc., if you want to activate it.

A/C control is optional and you can find those components locally. Worry about that later. Most of the time you don't need it because it can be compensate with proper mappings for idle.

Limitations:
What do you expect from a stand alone? Usually no limit but you can program it to have the limitations such as rpm limiter, boost limiter etc. You can even control NOS with MS if you want. You can also fit that ricey MIVEC head and use MS to take the command of everything. what more can a standalone ecu do?

p/s=a demo vid for viewing http://www.youtube.com/watch?v=A8NqFl0qzBM