2004riotuner turbo'd his Rio with a GT28R @ 15psi and a Megasquirt Stand alone. Then on another forum a guy named Virgo also turbo'd his with a VJ11 turbo at 7psi and an Apex'i SAFC. Then theres Sportage4x4 on same forum who turbo's his A6D, then swapped in a B6T from a 323 GTX at 20psi(made 250HP, in a Rio!!). Then the first person to ever turbo a Rio, BPEstilence, on that same forum, did it with a stock ECU at 5psi, and then switched to a Megasquirt and upped the boost. Out of those, Virgo is the only active member, with a currently rebuilt engine.
From the info I gathered from them:
You can put a turbo on the stock engine/ECU up to 7psi. Suggested that you put Mustang 19# injectors (same style plug).
EVERYTHING has to be custom made. You will more than likely have to lose your A/C and P/S (although virgo still has his, but being restricted to the VJ11 Turbo).