Higher compression 12:1
Got it - sorry about that.
Hmmm. One of the hallmarks of the EcoBoost line is the integrated exhaust manifold. That is the exhaust manifold is integrated into the cylinder head so that it can benefit from the engine's cooling system, but I have never heard of an integrated turbo. This would imply the exhaust manifold and turbo are a single, integrated, part. I believe the turbo and exhaust manifold are still separate parts on the 18+ models.
For the 2015-2017 MY the exhaust manifold is integrated with the head, not the block. This is the engine block:
It's all trade-offs. You might get better exhaust flow with a header, which might produce more horsepower, but moving the turbo farther away from the head will reduce response time. More horsepower is great when you keep the engine up around redline, but turbo lag reduces power down low, where a street car engine spends most of its life. That would make the car less driveable.
What benefit do you see with a header? As I understand it, no matter what you do with a turbocharged engine the turbo will impose a flow restriction on the exhaust. In the bad old days the biggest exhaust issue for turbocharged engines was reversion. With the exhaust system pressurized between the cylinders and the turbo there is a danger that a portion of the exhaust from one cylinder just beginning its exhaust cycle may be forced backward into the exhaust valve of another that is just beginning its intake cycle. Increasing the length of the exhaust runners via a header helped cut down on this problem via momentum. For reversion to occur with a header installed the exhaust pulse from one cylinder will have to push all the way down its own runner and all the way back up the other cylinder's. The twin-scroll turbo system in our cars are all but immune to reversion because the exhaust pulses of cylinders that overlap are divided from each other. Given that, I'm not sure I see the benefit of a header unless you use a different turbocharger.
