OK, I left the MAF and VE table stock and played only with the IFR (logged LTFT's vs. MAP).

The IFR table is now a curve with a little higher values at low MAP.
The LTFT average is around zero +/- 2%).
The car itself drives as usual but the LTFT are more consistent. Tuning the MAF curve they changed depending on the driving time and on the wheater. Now they remain pretty constant.

The STFT's used to bounce up and down a lot (+/- 7-8%). Now they are about +/- 3%.

The big surprise is the fuel consumption: On the highway at constant speed it used to be much better than on country roads. Now it's about the same. I mean: on countrie roads it needs as "low" as on the highway! This in winter and during short trips.