gyro drift

Alright, so I got a KK2.1 Hardcase and I put it on the HK x650f quad frame with AQ2810-750kv motors, HK BlueSeries 30A escs, 12x4.7 props. Running a 4s 4500. Getting around 15 mins hover. On stock firmware it was horrible. After upgrade there was an enormous difference, almost hands free hover...