mamba 25 hiccup?

[jokerjustin]

well ive had my rc18t for about 8 months now and its powered by a mamba 25 and 8000kv motor.. ive always run it with a 2 cell lipo and ive never had problems. but recently ive had the urge to get more speed and now when i get to about 75 % of power it stops responding and starts steering itsself till i run and catch it... i thought it might have been my reciever messing up so i bout the jr xs3 pro tx/rx and im still having the same prob..? the only way i see this happening is that my bec cannot keep up... any ideas?