See below regarding immobilizer on address 05
http://wiki.ross-tech.com/wiki/index.php/Immobilizer
Which cars have Immobilizer?
In the US/Canada, most VW/Audi models prior to model year 2000 did not have Immobilizer.
In the rest of the world, Immobilizer usage was introduced earlier.
In most vehicles the Immobilizer Control Module is integrated into the Instrument Cluster.
Upper Class Vehicles like the current Audi A5, A6, A8 and Q7 have a separate Immobilizer in Address 05 - Acc/Start Authorization.
Many of the older non-US market vehicles as well as some US-Market VW Golf Cabriolet (1E) and VW Transporter/Eurovan (7D) have a separate Immobilizer Control Module Address 25 - Immobilizer