In my opinion, finally the culprit found. In march 2023 while coming back from a leisure trip of 2300 Km in 3 days, it lost all power and acceleration and huge steam coming from behind the engine between the head and engine block ---head gasket leak. The gradually increasing the slow coolant leak was there, for the last a few years. The leak was into the cylinder No. one which started causing intermittent P0301 see also
https://www.automotiveforums.com/vbu...hp?t=1158769it. During the repair work it was found that he heads were repaired during the repair of pervious head gasket leakage. These differed in the thickness slightly, and now these were irreparable. I bought the two heads from the junkyard. These were almost new. Now the STFT and LTFT is very nearly equal it differs only by 1 to 3 at the most. It runs well no code and improved mileage by two Km/ litre