been having a problem with my buggy

[Hyper-5]

my current setup is Xerun 150A ESC, speedpassion motor 3.5t, and one 11.1v 8000mha 20c lipo, even when the car is off the ground it still does this problem. when l give it full throttle when stationary it sometimes goes full throttle nd sometimes its half the throttle, then when l try to steer or brake, it wont let me and l have to wait for about 3-5 second for it to respond, when doing my speed runs and hitting 99km/h it frightens the shit out of me when it delays in brakeing or turning. l've crashed once under a car and bent the chassis because of this issue