was thinking is there any way to add an immobilizer to the b5 platform using an A6 ecu that has the serial eeprom in it.  Will probably need a portion of the ignition switch and also a new key with a chip, just curious if it will be possible.  Would be a good security feature for the older cars that tend to get jacked too often.

I think you could probably enable the immobilizer between the ECU and cluster to prevent people from switching out either of those two parts. But adding immobilizer support for the key would definitely require replacing parts. All comes down to price and availability of parts I guess.

Why has this stalled? I no one interested in making their S4 harder to steal?

yea i still have interest in this also, kinda why i posted the topic.  Does anyone have access to a Bentley manual for an A6? i want to look at the wiring diagrams to see what is going on.  I know on the earlier models there is a dash module which interfaces to the ecu and the key. 

Take a look at this page, pretty easy to put the rfid pellet in our keyfobs don't already have one in there, im going to take a key apart when i get home to see if it actually does.
http://www.myturbodiesel.com/1000q/a4/vw-smart-key-remote-replacement.htm

http://www.autotronics.co.uk/cscart/images/detailed/0/29897_29896_10_Audi_Immobox_Delphi.png

im not even sure if you need an a6 or ar ecu, think if you flash the serial eprom from an AR or A6 one and put an a6/ar 800bb bin back you will be ok.  I was messing with an ar ecu last night and it seems that all the coding is in the eprom for the immo cause i tried to bench flash it and it would not take, i flashed the serial with an m box serial and i could flash fine.

I was going to try flash a spare m box i had to see if it would think it had an immobilizer on it.

I dont even think you need the cluster to do this mod, the cluster is more of just the status indicator i think for the early models. 

Im really thinking this will be easy as the dash immobilizer box is all K line controlled, so you can pretty much interface it anywhere there is a k line.  just need to get the wiring diagram to see what else goes into that box.

Also how to pair the rfid in the key to it.

I have acquired another part of the puzzle:

My guess after a quick look for the coil

Ign coil (D2) pin 1 > grn cluster plug T32a pin 2, grn wire
Ign coil (D2) pin 2 > grn cluster plug T32a pin 17, blk wire

Does anyone know how to confirm what version of IMMO a 2002 allroad has?

I have read that if the cluster via VAG-COM diagnostics shows the vehicles VIN it's IMMO III and if not it's IMMO II. Is this correct?