PID and Motor upgrade

Does anyone have the experience of upgrading their PID and motor? I have two filastruders. One have a bad temperature control over ± 5 degree. I am wondering if I could find any PID with very stable temperature control? As I am trying to extrude composite with high load micro-ceramic particles in polymer (PVDF), I found the torque of motor is relatively small even I changed the current. Does anyone have upgraded their motor? Thanks.