Trying to get more torque on that 4L V8...

I uploaded the file for that engine. Basically a 4.0L V8 to put in a high-end sedan (something like a 550i). This one is naturally aspirated but I'm planning to make a turbo version for something like an M5. I have a lot of hp but I feel like the torque is lacking... How could I get more of that? Also, do you guys see anything else I could improve? Like emissions or economy.
Thank you
Edit: I finally managed to take a screenshot, apparently you can't take one in fullscreen...
Thank you

Edit: I finally managed to take a screenshot, apparently you can't take one in fullscreen...