Congratulations on your return to the garage.
Since it ran well before the fire…
During the rebuilding what parts changed out and to what extent the damage that would have contributed to the malfunction.
Could be a missing vacuum hose or leak somewhere, hence a combo of bad timing, idle and mixture trying to compensate.
If so then that’s where the focus should begin backtracking.
During the storage period it’s common that maybe a rodent built a nest under the engine shroud impeding air flow.
The hard lines under the passenger side could be for a trombone cooler or rubber hoses being from AC