Do you have remote start? Might try that. Had a similar issue (but no tune), no prime with foot in brake, but car would start with remote. Re-seated all the fuses and wire harness connectors on the BCM, and the issue went away.
Check the connections (fuses and wiring harness plugs) on the Body Control Module behind the passenger footwell kick panel.
A few months ago, my 2017 GT Convertible intermittently wouldn't start (maybe once every several weeks). It would crank, but not fire. Usually, it would fire after...