That may help you out...because efi live is classifying these as RC's they have not been putting updates on there website... im not sure of the reason behind this... but that is the most up to date version (build)
Until we have a stable version of our next full release we won't be updating the website. The RC software began as BETA, and was then named as our release candidate because it was deemed stable enough for release. We've made a few changes since then to get to RC5, however it looks like RC5 is stable enough that it will be our next full release.
In answer to the original question about the unrecognized ECM - for Duramax there hasn't been any new OS's in the last 6 months or so, so running build 88 would be fine EXCEPT for LBZ/LMM DSP. If you are running LBZ/LMM DSP you will need to install the RC software from our forum.
You should also note that because we write to different areas of the ECM for LBZ/LMM DSP you will receive that error message when you try to read out a DSP tune.