One of the things that I have found during this swap and driving the car with this setup is that the 16v in general runs much hotter than my 8v ever did so this led me to thinking about the Digi2 system and how it would react to these higher temperatures.
As we all know the Digi2 ECU is heavily reliant on the Coolant Temp Sensor.
In fact the Digi2 ECU makes most of its fueling decisions based on the input from the CTS, (as well as the VAM and intake air temp sensor ).
The Ignition is also is influenced by the CTS which brings me to what i wanted to talk about.
Think of this... when your motor is hot then so is your cylinder head and combustions chamber's. When the motor is hot their is more chance of preignition and pinging. The CTS senses this heat and tell's the computer and ignition to retard the timing to prevent this, as well as leaning out the fuel mixture.
Another way to think of it is that when the knock box hear's something bad it retards the timing.
So in conclusion: Hot motor equals retarded timing and lean running.
I highly recommend the use of a lower temperature thermostat and lower temp radiator fan switch to keep the motor cool and running strong. Another often overlooked sensor is the fan afterrun switch which tells the fan to come on when the car is turned off and the underhood temperatures are high. If this switch is not working it can cause hot start problems caused by heat soak.
I have heard that redline water wetter destroys VW water pump seals however I have never tried it so I can not say if that is true.
On another note I have been toying with a device for Digi2 that will control the signal from the CTS and give us some adjustability in terms of the air fuel ratio. I have tried adjusting the VAM spring but I am more interested in something that can be more easily adjusted for tuning purposes.
I will update you when I have tried a few of my ideas.