edited above

Yes to the 123, most stock cal's are like this!!! The engine will always respond better with the slightly richer mixture while the computer attempts to remove fuel rather than add.

Are you using the EGR circuit?
I haven't followed this thread closely, can you post the stock .bin you started with so I can find stuff? Most stuff I have seen can usually accept 5 more degrees of...

Yes, I'm not sure LT1's ever had an EGR circuit that was active, however, all other ecm's have quite a few separate "tables" when the EGR is active. Or I should say, when the ecm thinks the egr is...