One add-on in the fluid domain that comes to mind is this part. It does not add that 700 HP however it definitely helps in scooping a tad bit more air to the intake at both low'er and high'er speed, and helps cooling engine compartment (opposite side). I believe this could be a nice 3D printed item; not requiring a whole lot of engineering (cfd modeling-wise), easy to surface finish, "and functional", etc.
Apologies for the low resolution picture. If you need more just ask and I'll see what I can do for you.
