Has anyone done a Unitronic 2+ w/is38? My setup, just finished this past weekend:
Stock air filter (aFe on order)
Stock air box w/snow guard removed
MST tube & elbow
is38 (duh)
Stock exhaust
Stock intercooler
I know I'm leaving some power on the table but I was a little underwhelmed so I logged a 3rd gear run and was surprised to see boost peak at 1.4bar, barely more than the is12 with the Unitronic 1+ (2.25bar). That's about 21psi.
It pulls really hard eventually and doesn't trail off. I lifted at 6250, unfortunately.
Can't speak specifically to your setup but, in general:
Larger turbos will add less heat to achieve the same pressure (they're not working as hard). Obviously within reason.
Larger turbos won't have the same shocking torque as a small turbo (so it might feel underwhelming when in actuality, it's just smoother).
Larger turbos will obviously be able to support more boost higher in the rev range (since they're capable of flowing more volume).
The difference between the is12 and the is38 isn't HUGE but it's there.
Someone else probably has more relevant/technical data.