I was just reading over the pages of this post and thinking about a couple things.
I read Burnall was having problems when hitting the gas, while I think it will help your idle by replacing your ICV, I suspect the rest of your problem could be your crank position sensor (this is what ignition is based upon in our motronic 1.7, i THINK, not 100%) however I had hopes that your fusebox underside fix was going to be the cure.
Also, Mark D (EAT in Canada) has a service that does ECU fixing, I did not see ours on his list, but who knows.
I had a weird missfire issue about a year ago, car would start cold, warm up and run well.
After an hour of running (seemingly long time) the engine would missfire at ~4600 rpm, almost seeming like hitting fuel cutoff/engine speed limiter.
As long as you didnt rev that high, it would be fine, no matter of the throttle position.
Over a few minutes more time, the missfire would drop to ~3500 start doing it at that RPM as the engine was warm.
Replaced: Plugs, Wires, tested all 4 coils. No fix, then replaced camshaft pos sensor, this seemingly fixed it for about two days, then it was back.
FINALLY, RESEATING my ECU connector in the glovebox (just taking it off, and putting it back on) fixed the problem.
Strange world here
