Thanks Tibibond!
Unfortunately DME is MSD87.1, so no solution for reading ISN from it at the moment.
What I'm trying to do is to update a 523i to 528i power level just by changing intake manifold and program DME...but there's the power class issue, so I bought a used 528i DME, CAS and key. So I had to play with both CAS in order to get it to work in it's full glory. Eventually I also figured out that ZGW reads CAS4 VIN and messes up the whole FA resulting in numerous equipment errors.