I have experimented with this feeling of lag and have in my opinion found that the torque of the diesel moves through the gears quite quickly and holds in high gears, so when you approach a corner or a roundabout you think you have nearly coming to a halt but you could very well be in second or third gear which means you are in a low rev range and yes I have driven the petrol version which feels like you are not suffering the lag as much because it drops down a gear and holds a gear longer going up.
In my experiment, I played with manually holding the vehicle at 2000rpm for whatever the situation was, like coming into a corner and coming out, it is in the rev range that has no lag and punches on quite well...it is not for my normal driving but if you want to move a little faster it works...I am running The Ultimate set at 5...seems fine for me