i dont want to rain on your day but i've had quiet a few dsm's, im one of those guys that never learned his lesson when it came to those cars and i dont think you've thought this quite thru....but i've had a couple 20g turbos, had one that made 390awhp on a talon too....couple things i dont think you've taken into notice. People go with the garrett turbo's because they are bigger, take longer to get into boost and have spool somewhere around 3k-3500rpms where the cam driven fuel pump really starts to kick in. To the best of my knowledge we dont have a competent tuning and fueling solution for the ms3 as yet so putting a rediculously fast spooling turbo on a ms3 is asking for problems.
And before anyone tries to equate the spool of the 20g to the k04, even a reworked unit....dont. yes they might spool fast but that 20g moves more mass....and with no fuel or timing control, you might as well throw a grenade under your hood and start booking. Im not saying it cant be dont, its just one hell of a risk because of the notorious quick spool of the MHI 20g and our lack of fuel control.
but anyway, good luck with the project.