Made an account just to answer this cause ive been doing a lot of research on this car.So why all the massive torque under 3.5 K ? The skyactiv head and exhaust headers ?
Is what is maximizing torque and HP under 4K also restricting the engine above 4k?
They created this weird down pipe/ turbo hybrid called dynamic pressured turbo that allows boost build up at 1k revs. This is then released and causes a huge amount of boost/torque. Then there is actually a huge cut off. Its good for track racing where you can get going fast after turns but not really good for drag. This engine was suppose to be put in the MAZDA TCR but they decided to put a nonproduction engine... That might be a bad sign. I also own this vehicle.
Here is a video explaining the science