DIY EFI had the leasn cruise working on GM V8's a couple years back. IIRC, they cycled it on/off so as not to get things too hot running too lean too long.
I'm not sure of all the specifics but I thought that the stock code took care of the cycling. I seem to recall reading a description where the the O2 sensor was "put to sleep" during a steady state cruise and would wake up from time to time. Interesting concept anyway. I'm going to enable mine once I get the ECU tuned.
No, as I recall hearing it, the code was there but it never gets to it. Essentially its disabled. I haven't followed that list for a while, but when I did, a couple years ago, there were people trying to implement it.
Yes, it is disabled from the factory but all the code is in place. To enable it just requires you to set the flag to true. Sorry I wasn't very clear in my earlier post.