The power of the motor will increase over the next several hours as the motor breaks in.
But his will have no effect on the hydraulics.
As far as lifting power, as already stated if the bucket is free from the pile you should be able to lift the dirt. Now if it won't lift the bucket full of dirt while the bucket is still part way into the pile that is very common and understandable. While in the pile not only are you lifting the full bucket but also all of the dirt above your already full bucket.
steve