[cbuffhm]

Makes sense theonewithin. Is there a more proper way to unplug after a tuning session?

Also, I did a clear of the EEPROM, then a read of it to verify it was cleared, reloaded firmware then the tune and the Baro issue was fixed. All is well now!

[theonewithin]

Best thing you can do is cut the red power wire from your tuning cable so it doesn't power the Arduino when in the car

[cbuffhm]

I have a SpeedyEFI PnP unit with just a USB A (laptop side) to USB B (ECU side), so I am not sure if I have the red cable you are referring to, unless its something internal or I am just showing my non-proficient electronic side

[theonewithin]

Cut the red WIRE not cable.

You remove the sheath from your cable and cut the red wire. This stops your laptop/desktop whatever from powering the Arduino.

You could also remove the pin from the USB connector on the Mega too if you prefer that option.