You can do different things with COS 3 or 5, I believe, to have a something of a commanded lean-mode for cruise conditions but the real "lean cruise" is not there, and the guys have clearly (and wisely) stated that they will NOT but it in a custom.

I remember someone (Tordne, maybe?) spending a few minutes in another "lean cruise" thread, talking about how he approached it.

At some point, I'll likely move to COS #5 but at this point the MAF still does it's job nicely for me - and since my '04 GTO has lean cruise, I figured it out and have made it work for me. I'll be the first to admot, though, that it's a little quirky...