Originally Posted by Amnizu
+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.
This. A FMIC doesn't "add power" per se, rather it allows the car to hit timing targets under high load conditions for extended periods of time. I'm not sure if the 1M has a different intercooler, but the stock N54 unit is a piece of crap. If you plan to tune, a FMIC is a necessity, imo. Even running relatively tame mapping, the car will pull timing very quickly if the intercooler can't stay efficient. An upgraded intercooler allows tuned vehicles to hit significantly more aggressive timing targets, and if you plan on tracking the car even w/o a tune it's a no brainer. A very worthy upgrade for an engine that runs HOT. I would also add that at least in my experience, the power "gains" are apparent in the mid range, not just up top.