I wouldn't count on finding it at #9-ecu and #26-cluster, since that's the A3 spec. There are threads on tdiclub, where guys have put Euro clusters with MFA in their A4, so that signal must be present, and i assume, pre-wired in the harness.
edit: maybe it's not pre-wired. i see a shopping list for the conversion, that includes "repair wire from the dealer", so maybe wires do need to be added.
edit2: from
http://forums.tdiclub.com/showpost.p...&postcount=420
32-Fuel consumption/vacant/Radio-Navigaion enable
Maybe it's #32 on the green 32-pin connector?