Fiesta 1,4i cat 1991 hell on earth

Im having trouble with a Fiesta 1.4i cat cvh 1991 with EEC-IV.
Runs smooth on the road at higher speeds, fuel consumption is high and engine is lazy especially at low engine rpm.
But the big problem is driveability at lower speeds, when stopping at the lights the engine dies for a split second when letting go of the accelerator. The car jumps lika kangaroo and is very nasty to drive in the city because of this.
But, after having disconnected one battery lead, so the ECU "forgets" what it has learned, and connecting it again, the car runs just fine for a day or two. No jumping, runs smooth, good power at low rpm:s. So it seems the ECU learns bad habits after a few runs.
I have a LED in the dash monitoring the output of the oxygen sensor (HEGO, it turns on at about 0.4V), mostly it blinks like it should but sometimes it just is on for a hundred kilometers or more. So there is some instability in the system, but where?
Have changed the ECU, MAP, HEGO, EDIS, TPS, PIP, Ignition coils.
Have measured the output from the TPS, ECS, ATS, MAP, VSS continuosly during driving and they are OK, no intermittent failure there.
The engine should be in a fairly good shape otherwise, its been driven 120.000km and the valve oil seals are also changed so oil consumption is nearly zero. No air leaks in any air hose or exhaust pipe before the HEGO.
One thing I havent checked yet is the fuel pressure and the regulator on the "carb". Guess the fault must have to do with these things.
Or, any suggestions? Or is it best they come and take me away, to the funny farm..
TIA,
Magnus
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O, and I HAVE triplechecked the ICV, the motor and the switch in it ARE working fine.... (funny, people call it a stepper motor, it isnt a stepper motor, its a regular DC motor....)
Magnus

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Seems there are only pros responding to the messages here... just look at the amount of replys Ive got... Sad......
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Well, sorry....
Most dont respond if they have nothing new to offer. You've covered much of the ground, already.
But I'd go with the fuel regulator, next.. since you seem to have covered most other possibilities. And if the LED staying in one state corresponds with the poor performance, I'd say that's a pretty good bet.
That... or a poor ground connection
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And maybe 80% of the people here are from the US or Canada
Not to many fiasco's here, especially with 1.4 engine, they use those for there lawnmower

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