Its a tiny turbo.
I believe its like a TD-04 13T(used in the 93 V6 aero) or something silly like that. They could have gone bigger, and should have.
Yeah, T5.2 its -.3 better then the rest.
1989 900 SPG: Trionic 5(stg1), Aero seats, TD04-15G, 3" Turboback. SOLD
1993 9000 Aero: 3"Turboback, T5Suite Stg.3