I used vwtool too, but got the same message. Is it definately pin 20 on the ECU?
I set the ignition timing and idle speed when in service mode. It idles really low now, about 600-650, but seems quite steady.
The symptoms have now disappeared, and what's happening now is it takes about 4 or 5 cranks for 10 seconds each before it will fire. I can hear the pump prime each time I turn the key. If I've been driving for a while, then slow down to idle and stop, it will idle at 1500-1200-1000, staying at a few seconds for each until it settles at 650ish.
Also, when I move the ECU multiplug, even slightly, the relay for the fuel pump clicks on and off, as if the contact is making and breaking. At one point, I wiggled it and the starter motor fired. Luckily it was in gear and handbrake on so no damage.
I have cable ties keeping the plug securely onto the ECU, but I'm assuming it may move about when the cars moving.
If you maintain a steady throttle to keep at a set speed, it feels like the car is kind of pulsing, as If trying to accelerate.