P4 is the running dark horse for IR. It is also a high speed loco which can pretty easily hit 130+ with a 24 coach load.
I am a regular traveler of this train starting from 2011. I had seen the ages of P7 and now seeing the power of P4 too. There is absolutely no difference in performance with a loco link change for this train.
I had traveled this train last month only while returning from Delhi. What a superb and powerful performance by that Hwh based red best, just aswm.