It really doesn’t matter how much HP the car makes, or how big the fuel pump is, or how large the injectors are really. The engine is still only 2.xx liters and the required fuel for cruise shouldn’t be much different. Yes, the pump/s move more volume and yes the injectors will flow more fuel but they should be open a fraction of the time and the rest will find it’s way back to your tank. E85, will 100% make the mileage go down…not arguing that.
FWIW, my 200 got 23-25 in stock form and on a recent trip to Carlisle, PA with an 044 pump, injectors twice the size of stock and making at least double the power it made from the factory and I got 29-30mph highway.
What is your cars lambda/afr at during cruise?