The S80 T6 used a very similar engine with twin turbos, I believe the
compression was lower and a different engine management system.
Personally I'm a big proponent of turbos, they're much more elegant and
efficient. I think your best bet would be to find the T6 motor and use a
custom fuel system like Megasquirt, or at least use MS on the motor you
have. Adding a turbo requires some special considerations so you don't
blow the motor. Motors that came with a turbo to begin with are a better
bet.
