Originally Posted by KennyPowers
the most gains will be seen from a tune where the tuner will be able to push the car a little harder and hold more boost to redline because of the more efficient cooling capabilities.
+1. On a stock core at high rpm the turbos essentially become hot air blowers. The larger core allows the tuner to push the operating efficiency range of the turbos a little bit further. We're talking in the last 1 to 2k RPM range.
So as others have said, unless you've done supporting mods, (downpipes, software, and possibly intake) to make that extra top level horse power possible just adding FMIC won't do much for you and may even make you a bit slower.