After replacing all my servos on my b400 to hi tecs i have now found another problem

I centered my tail servo no problem.

When the gyro has initialised my rudder control does not act how it should, i give rudder one way and tail servo returns to center, i give opposite rudder and upon releasing the stick it creeps back to near center but never gets there.

When i spool up the head i get yaw, if i counteract this the heli spins wildly out of control. If i reduce throttle the same thing happens, tail spins and spins

I am wondering if its not actually the servos but the gyro ?