I think you may find that this is quite normal until everything settles down after a few hundred miles. Is the fuel tank full for example? If not, the extra weight of 8 gallons of petrol (1 gallon of water weighs 10llbs) is the same as carrying someone dainty in the boot.
Compare my "lowered by 15mm" Greentech (or BlueMotion Tech in VW speak) Skoda Citigo to an ordinary (non BT) VW up! and you'll see that there's not much difference especially when you consider that both cars in the photo have 15" wheels/tyres. My car was only 3 weeks old when I took this photo but even now 15 months later, I haven't yet covered 2,000 miles so at the time of the photo it had probably only done 500 miles at most.
Although this is a large photo, it looks small in this post and sadly, clicking on it doesn't make it any larger.
Edited by: Robbyrook