basically in 3rd,4th or 5th gear if you floor it the ECU injects extra fuel for overtaking or short bursts of acceleration.it has nothing to do with turbo pressure as the name might suggest.only on the 1.6 HDi engines at the moment.
And, of course, new 2.0 HDI has the same feature. It is going to be installed in facelifted C5, Peugeot 407 and some other models of cars within the PSA and other manufacurers (Ford, Mazda, etc.)
Oh, so that is what it is! D-Jetronic on my DS does this - it is called a 'full load switch'
So do most carburettors whan manifold vacuum drops to atmospheric.
Nothing new - a triumph for the marketroids [}:)]