last 5 months:

the car runs fine when it's cold. After 5-10 miles (not always though, but 3 days out of 4) it feels VERY "nervous" running at fix speed. It's twitching, and pressing the speeder here, I have no power. Pressing the pedal fully down for 5-10 seconds,(during this time, the car is still twitching a lot) the power comes, often very abruptly. When the car start behaving like this, the idle (at red light) are unreliable. Can be ok, but often just the motor cuts out.
Starting the engine again if it stops, the idle is okay again, but at the next red light, it can be either good or bad again...

Also worth mentioning, is that this behaviour above, is totally independant of the weather, temperature, rainy / sunny, so I have not replaced the spark plug cables or the coil (since if these are bad, it's ofter worse whan damp weather).

Changed spark plugs, fuel filter, looking for cracks in air hoses (visually, and with start spray).
Added a bottle of injection cleener in the fuel tank.

Thorougly leaned air mass sensor and the idle control valve. Have checked the throttle position sensor with multimeter, checked the ohm slowly over the full scale.

And all above, absolutely not the slightest improvement...