Transmissions question (ZF 5 speed)

[X5UK88]

Hi guys,

I've noticed my X5 will accelerate better under part throttle when down low in the rev range as opposed to flooring it. If I give it part throttle whilst just cruising in say 5th it'll pick up smoothly, if I give it almost full throttle before it drops any gears, I almost feel a bit of resistance and it doesn't go like it would on part throttle, then it'll start to take off over 3k ish if I remember rightly.

It's quite hard to explain hopefully I've got it across.

Is this normal behaviour or does it sound like an issue of some sort? Or could it even be the engine?

Thanks in advance for any replies.