I've been searching the archives without any luck regarding the compatibility of a C5 RS 6 instrument cluster in a B5 S4. It seems that there are a couple of potential hiccups...and I'm hoping you might have some answers for me. Here's what I've learned.

There seem to be 3 configurations of the immobilizer in recent Audis.

1) No immobilizer. (like the B5 S4)
2) ECU coded immobilizer (Immo-2) which requires communication between the keys, cluster, and ECU in order to operate the car. (like a bunch of 01+ cars, like the B5 RS4 and some A6's)
3) Cluster coded immobilizer (Immo-3) where the functions are contained completely inside the cluster.

Configuration 1 seems to be great. The car will run without the cluster even installed, and minus a flashing light on the cluster, the car will run with a cluster from Config #2.

Configuration 2 seems to be finicky...you need the right combination of ECU and cluster, with VAG Com re-coding, to make it work.

Configuration 3 seems to be the highest complexity...without a dealer special re-code and a compatible cluster, you're SOL.

So from what I can tell, the RS4 clusters in B5 S4's are Config #1 with a cluster from Config #2. The cluster can't find the immobilizer, but the car doesn't care. I have access to a new, never coded RS6 cluster, which as far as I can tell will fit in my car and look great. I'm concerned that the strategy for installing an RS4 cluster won't work because of the immobilizer being built into the cluster. For one, I don't have any sort of expertise in the matter, and two, don't want to spend any more money on this project than I have to. Lastly, I'm fearful that if I try the RS6 cluster and it doesn't work, I'll have ruined an otherwise valuable cluster, and the resale value to the Audi (or Ebay) community will be very low.

Who's got some (ok, ANY) input on this subject?

modding is addictive....once you start, it never stops.