Where is peak torque

[ballo1000]

Afternoon, I have been driving the Maverick for a week or so now and just had a query. On my drive to work I travel along the A614 from Nottingham to Worksop, it's slightly hilly in places but 50 mph the whole way. On all the hills she doesn't have enough power to maintain speed and I have to drop into 4th at times. She pulls smoothly with no missing or juddering, so my query is, is 50 mph just below the torque curve, hence lack of power.

Thanks in advance