This happened 2 months after fuel economy went down from 14 L / 100 km to 16 L / 100km.

All maintenance is up to date. Serviced regularly with OEM fluids and parts.

Note: Valve adjustment was done a few months ago and valve cover gasket was replaced.

 

I'm confused as to how this is even possible to be honest. I'm sure you are aware that the turbo spools because of exhaust gasses, so how would the car spool up if your not moving (and I'm assuming) the engine is not revving?

 

Sounds like a MAF issue if the RPMs and Spool guage increase at a stop. Maybe try cleaning the MAF and see if that helps resolve it.