As expected with a centrifugal blower, the torque really comes on strong from 4000rpm upwards and the engine's still pulling hard up to 5800rpm. Thereafter, it noses over so there's no point going beyond 6000rpm. There's at least 400lbft of torque from 3200 to 5900rpm, so the powerband isn't as narrow as you might think considering peak HP arrives at 5500rpm and peak torque arrives only 700rpm lower than that at 4800rpm. An 11.5-12.0:1 A/F ratio is exactly what you need at WOT on a forced induction engine.