Keep in mind to run the cable throttle the base tube for these comes from an early 6.0 with cable throttle. Every thing is scaled up for the 8.1 for base fuel and timing tables. There was never a 8.1 from Gm with a mechanical throttle body so there is no base tube to go to when the L29 tb is installed they have to go with the 6.0 setup. And since the 8.1 is identical in the ecm/ controls as a LS the dbc conversion works fine.
I guess they could have done something different in the tune for the slush box but since it’s TH400 the ecm don’t have any trans inputs/outputs to worry about so it’s treated like a manual setup anyway. But I’m betting it’s the same tune as mine. As such, it makes me not doubt the tune. The idea of a leaky intake gasket still nags at my brain. It may just be internal in the valley instead of external where the carb cleaner would have found it.