[Subaru Alliance]

you can really mount a turbo anywhere you want to as long as it is in the exhaust stream. I haven't see it done, but you could replace your cat with a turbo (i'd be afraid of snagging it on a speed bump or something)

I can see how it may look as though it is gonna be super laggy, but really if you figure the length of tubing from an average turbo, through an intercooler, and then back to the throttle body, i'll bet this set up will only have a foot or two more tubing.