The VW's sensor has three pins assigned. One is constant ground. Between the second and the third - there's a constant resistance of 510 Ohms.
At this moment I've measured that on the cluster's pins there's 2,3V voltage. So... Maybe, it's not such a bad idea to use analog pins to write values to it?
My only caution would be to verify the cluster will operate with a 1K pot instead of the original 500 Ohm.I would expect the cluster to use the 500 ohm existence as a diagnostic.