Can any one help please?

Have my X5 3.0d 2002 year with automatic gearbox for couple of weeks now and I'm trying to sort few bad bits now

Driving in up to 2000 rpm it is like without any power, basically, when you start driving from 0 till about 2000 rpm is like you towing some elephant, but after 2000 rpm it is just like kick, and after 3000 rpm on highest speed (above 30-40 mph) doesn't want to go again, looks like the power is missing somewhere.

I tried new Airflow sensor - helps in middle range 2-3000 but before 2000 rpm and after 3000 rpm it is like 1.6 diesel just doesn't want to accelerate it.

Thanks for any help and sorry for bad English