slant 6 rebuild and upgrade list

Here are Mitsu and Garrett turbo maps galore....LOL. There are sets are in different flow formats (CFM, m^3/sec)
Stealth 316 - Turbocharger Compressor Flow Maps

(As you read this website, remember that the 3L V6 Mitsu engine being discussed uses TWO turbos so the flows are half what they would be for a single turbo application.)

I was looking at these last night for the 225 at the lower boosts; your 10 psi pressure ratio works out to around 1.7 BTW. I just looked a few over and it looks like one or more would map out well to those lower boost ranges and cfm's. You're roughly in the 260-290 cfm flow range unboosted at 5000 rpm depending on VE, and maybe around 300-350 cfm boosted/compressed flow at 10 psi (no intercooler). The 09G turbo is on the small side so would not get to that boost and flow at 5000 RPM. But it would have good boost at lower RPM's and would likely 'come on' pretty fast. It would be like what you might find on an older, simple production turbo'd car: not too likely or even possible to overboost at high RPM and blow things up.

The 13G looks like it would get closer to the flow at that boost; maybe a bit short but would 'self-limit' the flow/boost at 5000 RPM. It would have higher boost capability at lower RPM's. So a wastegate would be needed IMHO.

The 14G looks like would get you there for sure and you would have some capacity for higher RPM's too. (not sure that is all that useful.) You would have to limit the boost with a wastegate for sure. BTW this is the stock Mitsubishi Starion/Chrysler Conquest turbo for use on a 2.6L 4 cylinder. These engines had the wastegate set around 13-14 psi and used this (relatively) larger turbo on just 156 ci to be able to generate that boost level across a wide RPM range.

As for the valves, I was really meaning a wastegate, to control max boost. If you do that, then you can use a larger turbo and limit the higher boost capability to where you want.

The blow-off valve has a different function, to dump excess boost spikes when the throttle is closed rapidly while under boost; that prevents turbo stalling, keeps it spinning with the throttle closed for good response when you push on the throttle again, and helps prevent bearing damage. It is very useful if you are racing or rallying, or running the ridges hard, but perhaps less so on just straight line use.

Beyond the maps, which reflect just the basic turbo designs, I'll say again that a lot of the low RPM behavior is determined by the impeller wheel details; small tweaks and bends on tips and so forth can make a turbo really come on fast at lower flows. (As well as the cam.) That can make a larger turbo spool up readily at low RPM's similar to a smaller one. The Mitsu turbos have had a lot of development work and experimentation on them over the years for the Japanese cars, to get this type of response in special impellers, and so that can benefit other users.