Thomas,
1st .. find out if you ecu is "motronic" .. which I think it is.. I would have to go into Erwin to find this out .. and that costs me
A little searching will find this out...
http://en.wikipedia.org/wiki/List_of_Volkswagen_engines says that a 20V petrol using Motronic ME 7.5 electronic sequential SFI fuel injection... so that is sort of confirmed (wikipedia is never fully confirmed!)
Info I sent you ... shows Motronic to be all the petrols
So it is Motronic .. then fit the cruise kit ... as shown in the circuits I sent you.. if using the Seat kit do not fit the ECU wiring as it seems this is for single wire connections to ECU .. find and change it to the 2 wires to ECU as below (or is it 3?!)..i.e.
...the wire that connects all these together;
XS3 connector T6w on pin 3
Cruise connector T41 on Pin 29
Cruise connector T41 on pin 26
Motronic control unit connector T121 on pin 38
Motonic control unit connector T80 on pin 24
... but also I found connector T121 on pin 76 is shown connected on Motronic (only have part details of a Motronic .. )so there is some confusion in Erwin. need to go through these 3 pins on the Motronic pin connector table and decide which does what.
It may take some detective work to decide which connector on the the ECU is which .. I found out by looking at connectors... one had more connections that the other so you could work out which is T121 and which is T80 (Erwin helped)
It is just one extra wire they need to connect (i.e. the two I show above) ... it is shown in Erwin .. and a half competant auto electrican should be able to track this all down using Erwin.
If I had Erwin I would just go look all this up... but I do not .. it will cost to do this and even then this is all not guaranteed... it is all exploration I'm afraid.. the fun of being first and working in the dark
Hope that helps ... do a PM if you need more