PF No 2 of KPG is used only if required. That is when 2 trains are going to stop at KPG, then only PF 2 will hold a train.
general trend I observed is
1) if both the trains are equally IMP, then PF 1 will hold MMR bound train and PF 2 will hold DD/SNSI bound train.
2) IMP train will be...
more... put on PF1 and passanger/ less IMP train put on PF 2.