From what I can gather (not being a physics expert) in theory power is torque x rpm. However, in reality, the engine loses efficiency as the rpm increases and so the torque cannot be maintained at high revs. This doesn't mean that less bhp is generated, as the increase in revs compensates for this.
According to Fiat specs, the GP multijet 130 engine develops maximum (130) bhp at 4000rpm - well past peak torque. It's therefore at 4000rpm speed that you should reach the peak of acceleration. However, it will generate enough bhp at much lower revs than you'd expect from a typical petrol car and so you can get very good acceleration whilst changing gear at around 2000.
...Or have I got completely the wrong end of the stick?