2012 Chevy Suburban 5.3l with a P0300 code and a rough idle

2012 Chevy Suburban 5.3l with a P0300 code and a rough idle and flashing check engine light. i have a otofix computer and it shows cylinder 3 is the culprit
here are the things that was replaced on vehicle some from other shops all ACdelco Parts

Spark plugs and wires
coil pack on #3
new fuel injector on #3
intake manifold gasket
valve body gasket which fixed the oil leak
cam sensor
crankshaft sensor and relearn
throttle body cleaned
upstream 02 sensors replaced
New MAF Sensor

here are some test I’ve done
checked all grounds on the vehicle and cleaned them
compression test 160 on #3
leak down test on #3 at TDC no leaks out of intake or exhaust or oil tube
swapped coils spark plugs on #3 to #4 no change
tested wires from injectors to ECM for continuity and coil pack harness there are good
i decide to check the map sensor seemed fine but when i left it unplugged the P0300 when away and engine idled higher but sounded better but of course map sensor code came on
i tried replacing MAP Sensor part with no fix either but when unplugged computer shows #3 with 0 misfires but plug it back in and same P0300 but #3 is the only cylinder
fuel pressure looks good on scan tool
pulled coil on sparkplug #3 wile engine running and it sparks fine
checked fuel injector with test light and it blinks
checked CATS when 02 sensors where out with bore cam looked fine to me
im thinking the ECM is messed up what are your thoughts or ideas i can check for?