UKPassats

my b8 1.6 tdi for a few days now has been increasing the rotation to 1000/1100 by itself as if it were doing the regeneration but it is not, the instantaneous consumption does not go up, the engine has no errors and the mechanic says that the FAP is fine, what can it be?

the car is remaped since last july, but before it was in vw dealer to upgrade the ECU because of the nox problems, and since more or less december feel some slight hiccups at low rpm.