Went and did a quick comparison between my graph and Dave's. Interestingly both 2.5s, albeit a VF46 v VF52, drop off approx 110-120Nm from peak as you go up the rev range. Both peak at approx 3500 but Dave's drops off much more steeply.
I think there's a lot of the automatic gearbox effecting the shape of Dave's torque curve. Almost like a rubber band being twisted and then let off if that makes any sense.