Good A/F ratio and optimal timing should give you a pretty flat curve. I think little over on the rich side will give more torque. Lean on topend for more HP. I was told.
On my dyno, I had 200-217ft/lb torque from 3000rpm to 5400rpm. A/F started at 10:1(Lost about 10ft/lb), then 14.5:1 at the 5400rpm. Max turque happened @ 11.5:1 A/F ratio.