To give a bit more info:
Yesterday I observed that the car starts ok, does the high-idle sequence (1000-1500 rpm) ok, then idles ok (about 800 rpm) but as time passes, idle is getting lower and lower (car runs perfect). It is not related to engine coolant temp, as the car cycled from 80 to 100 deg several times but the idle reduction was constant. The exterior temp was 13 degree. When the car was running for about 20 mins, the idle was so low that I couldn't let the car idle because it stalled just every time.

Does this give any clue?

In the posts several stalling problems are said to be related to the fuel pump relay, but I think this is not the case with my car as it is progressive and the car runs fine without hesitations, etc. The fuel pump is noise, that's true. But a fuel starvation should manifest in the normal running, not only the idle, is that true?

Thanks!