Last year I bought an Audi A4 Quattro 2.0T. It is a decent car but not the best of its kind. Anyway, not knowing much about the engine specs, the drive was usually smooth but there was an unusual jerk every time when I just turned on the engine and started to drive. Or the same thing happened if I had been driving on a highway for a while and then got slowed down in a traffic jam to 20 mph, then drive fast after the jam and there is the jerk again. It just made no damn sense! And it was not a transmission problem.. Now I realize how this rough jerk/jolt is just because of the turbos, as per my web search the engines can get as hot as 650C, so idling makes them cool off and then when you start to accelerate again the rpm gets too high and the transition to higher speeds is not smooth. Whereas if you are driving at a constant high speed on the interstate or a constant slow speed in inner city driving, then you will experience just a smooth drive all the time.

Basically when the engine is run at full throttle and then brought to cool off, after that the transition to high rpms is not smooth specially if you are braking. Imagine something temperature shocked from 600C and then cooling off to ambient temperature of ~20-30C or something that is cool and then has to be heated up quickly, this temperature swing can be felt in the engine performance quite easily, at least in the A4s. Revving the engine for a boost helps with the heat soak, making the drive more stable.

Then again, I am not good with cars, this is just based on my observations and it might apply for any of the turbocharged cars.