2014 equinox awd
Tried to do a good deed and swapped an engine for a an elderly lady for free.
Having an issue with a 2.4 ecotec misfire.
Swapped in a remanufactured engine because only one had a dead number 2 cylinder 5 psi of compression,
everything went well with the swap. Car has 214k on it and new motor has about 60 miles on it now.
drove it around and everything worked no issues, gave it to the lady and she drove it about 20 minutes, now it has a misfire p0300.
Put scanner on it, cylinder 3 and 4 at idle, check plugs no signs of an issue, checked coils by unpluging them one by one with the car running did exactly what we all would think it would do the smoothed out once plugged back in, but still swapped them around to see if misfire changed in my scanner, no changes. Checked fuel pressures at idle 57 low about 450 to 480 hi.
pulled fuel rail and injectors. Swapped 1 for 4 and 2 for 3.
now misfire is no longer at idle and it is one 1 and 4 now but only under deceleration, i can rev and drive the car with no issues but when I let off the pedal 1 and 4 will misfire, once 4 reaches 80 misfires in a row the service stabilitrak comes on with a flashing check engine light, no engine reduce power, turn car off and back on code is p0300.

Just looking for some advice on where to go next or what information might help to troubleshoot this issue.
all sensors where reused from the old engine.

Thank you in advance
Landon